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authorLinus Torvalds <torvalds@linux-foundation.org>2009-12-05 09:52:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-05 09:52:14 -0800
commit607781762e7aae9c976f0a9a8829d4ba3e2da4ab (patch)
tree933dad6ecb0be49e9b1ef41b69d5aa256510720e
parentd0b093a8b5ae34ee8be1f7e0dd197fe4788fa1d5 (diff)
parent8bfb2f8e655b9d0c45fde679fcd5fd97e34513db (diff)
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Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (31 commits) rcu: Make RCU's CPU-stall detector be default rcu: Add expedited grace-period support for preemptible RCU rcu: Enable fourth level of TREE_RCU hierarchy rcu: Rename "quiet" functions rcu: Re-arrange code to reduce #ifdef pain rcu: Eliminate unneeded function wrapping rcu: Fix grace-period-stall bug on large systems with CPU hotplug rcu: Eliminate __rcu_pending() false positives rcu: Further cleanups of use of lastcomp rcu: Simplify association of forced quiescent states with grace periods rcu: Accelerate callback processing on CPUs not detecting GP end rcu: Mark init-time-only rcu_bootup_announce() as __init rcu: Simplify association of quiescent states with grace periods rcu: Rename dynticks_completed to completed_fqs rcu: Enable synchronize_sched_expedited() fastpath rcu: Remove inline from forward-referenced functions rcu: Fix note_new_gpnum() uses of ->gpnum rcu: Fix synchronization for rcu_process_gp_end() uses of ->completed counter rcu: Prepare for synchronization fixes: clean up for non-NO_HZ handling of ->completed counter rcu: Cleanup: balance rcu_irq_enter()/rcu_irq_exit() calls ...
-rw-r--r--Documentation/RCU/trace.txt254
-rw-r--r--Documentation/RCU/whatisRCU.txt2
-rw-r--r--include/linux/hardirq.h24
-rw-r--r--include/linux/rcupdate.h10
-rw-r--r--include/linux/rcutiny.h104
-rw-r--r--include/linux/rcutree.h7
-rw-r--r--include/linux/srcu.h1
-rw-r--r--init/Kconfig9
-rw-r--r--kernel/Makefile1
-rw-r--r--kernel/rcupdate.c122
-rw-r--r--kernel/rcutiny.c282
-rw-r--r--kernel/rcutorture.c65
-rw-r--r--kernel/rcutree.c465
-rw-r--r--kernel/rcutree.h69
-rw-r--r--kernel/rcutree_plugin.h309
-rw-r--r--kernel/rcutree_trace.c12
-rw-r--r--kernel/sched.c1
-rw-r--r--kernel/softirq.c2
-rw-r--r--kernel/srcu.c74
-rw-r--r--lib/Kconfig.debug2
20 files changed, 1234 insertions, 581 deletions
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
index 187bbf10c92..8608fd85e92 100644
--- a/Documentation/RCU/trace.txt
+++ b/Documentation/RCU/trace.txt
@@ -1,185 +1,10 @@
CONFIG_RCU_TRACE debugfs Files and Formats
-The rcupreempt and rcutree implementations of RCU provide debugfs trace
-output that summarizes counters and state. This information is useful for
-debugging RCU itself, and can sometimes also help to debug abuses of RCU.
-Note that the rcuclassic implementation of RCU does not provide debugfs
-trace output.
-
-The following sections describe the debugfs files and formats for
-preemptable RCU (rcupreempt) and hierarchical RCU (rcutree).
-
-
-Preemptable RCU debugfs Files and Formats
-
-This implementation of RCU provides three debugfs files under the
-top-level directory RCU: rcu/rcuctrs (which displays the per-CPU
-counters used by preemptable RCU) rcu/rcugp (which displays grace-period
-counters), and rcu/rcustats (which internal counters for debugging RCU).
-
-The output of "cat rcu/rcuctrs" looks as follows:
-
-CPU last cur F M
- 0 5 -5 0 0
- 1 -1 0 0 0
- 2 0 1 0 0
- 3 0 1 0 0
- 4 0 1 0 0
- 5 0 1 0 0
- 6 0 2 0 0
- 7 0 -1 0 0
- 8 0 1 0 0
-ggp = 26226, state = waitzero
-
-The per-CPU fields are as follows:
-
-o "CPU" gives the CPU number. Offline CPUs are not displayed.
-
-o "last" gives the value of the counter that is being decremented
- for the current grace period phase. In the example above,
- the counters sum to 4, indicating that there are still four
- RCU read-side critical sections still running that started
- before the last counter flip.
-
-o "cur" gives the value of the counter that is currently being
- both incremented (by rcu_read_lock()) and decremented (by
- rcu_read_unlock()). In the example above, the counters sum to
- 1, indicating that there is only one RCU read-side critical section
- still running that started after the last counter flip.
-
-o "F" indicates whether RCU is waiting for this CPU to acknowledge
- a counter flip. In the above example, RCU is not waiting on any,
- which is consistent with the state being "waitzero" rather than
- "waitack".
-
-o "M" indicates whether RCU is waiting for this CPU to execute a
- memory barrier. In the above example, RCU is not waiting on any,
- which is consistent with the state being "waitzero" rather than
- "waitmb".
-
-o "ggp" is the global grace-period counter.
-
-o "state" is the RCU state, which can be one of the following:
-
- o "idle": there is no grace period in progress.
-
- o "waitack": RCU just incremented the global grace-period
- counter, which has the effect of reversing the roles of
- the "last" and "cur" counters above, and is waiting for
- all the CPUs to acknowledge the flip. Once the flip has
- been acknowledged, CPUs will no longer be incrementing
- what are now the "last" counters, so that their sum will
- decrease monotonically down to zero.
-
- o "waitzero": RCU is waiting for the sum of the "last" counters
- to decrease to zero.
-
- o "waitmb": RCU is waiting for each CPU to execute a memory
- barrier, which ensures that instructions from a given CPU's
- last RCU read-side critical section cannot be reordered
- with instructions following the memory-barrier instruction.
-
-The output of "cat rcu/rcugp" looks as follows:
-
-oldggp=48870 newggp=48873
-
-Note that reading from this file provokes a synchronize_rcu(). The
-"oldggp" value is that of "ggp" from rcu/rcuctrs above, taken before
-executing the synchronize_rcu(), and the "newggp" value is also the
-"ggp" value, but taken after the synchronize_rcu() command returns.
-
-
-The output of "cat rcu/rcugp" looks as follows:
-
-na=1337955 nl=40 wa=1337915 wl=44 da=1337871 dl=0 dr=1337871 di=1337871
-1=50989 e1=6138 i1=49722 ie1=82 g1=49640 a1=315203 ae1=265563 a2=49640
-z1=1401244 ze1=1351605 z2=49639 m1=5661253 me1=5611614 m2=49639
-
-These are counters tracking internal preemptable-RCU events, however,
-some of them may be useful for debugging algorithms using RCU. In
-particular, the "nl", "wl", and "dl" values track the number of RCU
-callbacks in various states. The fields are as follows:
-
-o "na" is the total number of RCU callbacks that have been enqueued
- since boot.
-
-o "nl" is the number of RCU callbacks waiting for the previous
- grace period to end so that they can start waiting on the next
- grace period.
-
-o "wa" is the total number of RCU callbacks that have started waiting
- for a grace period since boot. "na" should be roughly equal to
- "nl" plus "wa".
-
-o "wl" is the number of RCU callbacks currently waiting for their
- grace period to end.
-
-o "da" is the total number of RCU callbacks whose grace periods
- have completed since boot. "wa" should be roughly equal to
- "wl" plus "da".
-
-o "dr" is the total number of RCU callbacks that have been removed
- from the list of callbacks ready to invoke. "dr" should be roughly
- equal to "da".
-
-o "di" is the total number of RCU callbacks that have been invoked
- since boot. "di" should be roughly equal to "da", though some
- early versions of preemptable RCU had a bug so that only the
- last CPU's count of invocations was displayed, rather than the
- sum of all CPU's counts.
-
-o "1" is the number of calls to rcu_try_flip(). This should be
- roughly equal to the sum of "e1", "i1", "a1", "z1", and "m1"
- described below. In other words, the number of times that
- the state machine is visited should be equal to the sum of the
- number of times that each state is visited plus the number of
- times that the state-machine lock acquisition failed.
-
-o "e1" is the number of times that rcu_try_flip() was unable to
- acquire the fliplock.
-
-o "i1" is the number of calls to rcu_try_flip_idle().
-
-o "ie1" is the number of times rcu_try_flip_idle() exited early
- due to the calling CPU having no work for RCU.
-
-o "g1" is the number of times that rcu_try_flip_idle() decided
- to start a new grace period. "i1" should be roughly equal to
- "ie1" plus "g1".
-
-o "a1" is the number of calls to rcu_try_flip_waitack().
-
-o "ae1" is the number of times that rcu_try_flip_waitack() found
- that at least one CPU had not yet acknowledge the new grace period
- (AKA "counter flip").
-
-o "a2" is the number of time rcu_try_flip_waitack() found that
- all CPUs had acknowledged. "a1" should be roughly equal to
- "ae1" plus "a2". (This particular output was collected on
- a 128-CPU machine, hence the smaller-than-usual fraction of
- calls to rcu_try_flip_waitack() finding all CPUs having already
- acknowledged.)
-
-o "z1" is the number of calls to rcu_try_flip_waitzero().
-
-o "ze1" is the number of times that rcu_try_flip_waitzero() found
- that not all of the old RCU read-side critical sections had
- completed.
-
-o "z2" is the number of times that rcu_try_flip_waitzero() finds
- the sum of the counters equal to zero, in other words, that
- all of the old RCU read-side critical sections had completed.
- The value of "z1" should be roughly equal to "ze1" plus
- "z2".
-
-o "m1" is the number of calls to rcu_try_flip_waitmb().
-
-o "me1" is the number of times that rcu_try_flip_waitmb() finds
- that at least one CPU has not yet executed a memory barrier.
-
-o "m2" is the number of times that rcu_try_flip_waitmb() finds that
- all CPUs have executed a memory barrier.
+The rcutree implementation of RCU provides debugfs trace output that
+summarizes counters and state. This information is useful for debugging
+RCU itself, and can sometimes also help to debug abuses of RCU.
+The following sections describe the debugfs files and formats.
Hierarchical RCU debugfs Files and Formats
@@ -210,9 +35,10 @@ rcu_bh:
6 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=859/1 dn=0 df=15 of=0 ri=0 ql=0 b=10
7 c=-275 g=-275 pq=1 pqc=-275 qp=0 dt=3761/1 dn=0 df=15 of=0 ri=0 ql=0 b=10
-The first section lists the rcu_data structures for rcu, the second for
-rcu_bh. Each section has one line per CPU, or eight for this 8-CPU system.
-The fields are as follows:
+The first section lists the rcu_data structures for rcu_sched, the second
+for rcu_bh. Note that CONFIG_TREE_PREEMPT_RCU kernels will have an
+additional section for rcu_preempt. Each section has one line per CPU,
+or eight for this 8-CPU system. The fields are as follows:
o The number at the beginning of each line is the CPU number.
CPUs numbers followed by an exclamation mark are offline,
@@ -223,9 +49,9 @@ o The number at the beginning of each line is the CPU number.
o "c" is the count of grace periods that this CPU believes have
completed. CPUs in dynticks idle mode may lag quite a ways
- behind, for example, CPU 4 under "rcu" above, which has slept
- through the past 25 RCU grace periods. It is not unusual to
- see CPUs lagging by thousands of grace periods.
+ behind, for example, CPU 4 under "rcu_sched" above, which has
+ slept through the past 25 RCU grace periods. It is not unusual
+ to see CPUs lagging by thousands of grace periods.
o "g" is the count of grace periods that this CPU believes have
started. Again, CPUs in dynticks idle mode may lag behind.
@@ -308,8 +134,10 @@ The output of "cat rcu/rcugp" looks as follows:
rcu_sched: completed=33062 gpnum=33063
rcu_bh: completed=464 gpnum=464
-Again, this output is for both "rcu" and "rcu_bh". The fields are
-taken from the rcu_state structure, and are as follows:
+Again, this output is for both "rcu_sched" and "rcu_bh". Note that
+kernels built with CONFIG_TREE_PREEMPT_RCU will have an additional
+"rcu_preempt" line. The fields are taken from the rcu_state structure,
+and are as follows:
o "completed" is the number of grace periods that have completed.
It is comparable to the "c" field from rcu/rcudata in that a
@@ -324,23 +152,24 @@ o "gpnum" is the number of grace periods that have started. It is
If these two fields are equal (as they are for "rcu_bh" above),
then there is no grace period in progress, in other words, RCU
is idle. On the other hand, if the two fields differ (as they
- do for "rcu" above), then an RCU grace period is in progress.
+ do for "rcu_sched" above), then an RCU grace period is in progress.
The output of "cat rcu/rcuhier" looks as follows, with very long lines:
-c=6902 g=6903 s=2 jfq=3 j=72c7 nfqs=13142/nfqsng=0(13142) fqlh=6
-1/1 0:127 ^0
-3/3 0:35 ^0 0/0 36:71 ^1 0/0 72:107 ^2 0/0 108:127 ^3
-3/3f 0:5 ^0 2/3 6:11 ^1 0/0 12:17 ^2 0/0 18:23 ^3 0/0 24:29 ^4 0/0 30:35 ^5 0/0 36:41 ^0 0/0 42:47 ^1 0/0 48:53 ^2 0/0 54:59 ^3 0/0 60:65 ^4 0/0 66:71 ^5 0/0 72:77 ^0 0/0 78:83 ^1 0/0 84:89 ^2 0/0 90:95 ^3 0/0 96:101 ^4 0/0 102:107 ^5 0/0 108:113 ^0 0/0 114:119 ^1 0/0 120:125 ^2 0/0 126:127 ^3
+c=6902 g=6903 s=2 jfq=3 j=72c7 nfqs=13142/nfqsng=0(13142) fqlh=6 oqlen=0
+1/1 .>. 0:127 ^0
+3/3 .>. 0:35 ^0 0/0 .>. 36:71 ^1 0/0 .>. 72:107 ^2 0/0 .>. 108:127 ^3
+3/3f .>. 0:5 ^0 2/3 .>. 6:11 ^1 0/0 .>. 12:17 ^2 0/0 .>. 18:23 ^3 0/0 .>. 24:29 ^4 0/0 .>. 30:35 ^5 0/0 .>. 36:41 ^0 0/0 .>. 42:47 ^1 0/0 .>. 48:53 ^2 0/0 .>. 54:59 ^3 0/0 .>. 60:65 ^4 0/0 .>. 66:71 ^5 0/0 .>. 72:77 ^0 0/0 .>. 78:83 ^1 0/0 .>. 84:89 ^2 0/0 .>. 90:95 ^3 0/0 .>. 96:101 ^4 0/0 .>. 102:107 ^5 0/0 .>. 108:113 ^0 0/0 .>. 114:119 ^1 0/0 .>. 120:125 ^2 0/0 .>. 126:127 ^3
rcu_bh:
-c=-226 g=-226 s=1 jfq=-5701 j=72c7 nfqs=88/nfqsng=0(88) fqlh=0
-0/1 0:127 ^0
-0/3 0:35 ^0 0/0 36:71 ^1 0/0 72:107 ^2 0/0 108:127 ^3
-0/3f 0:5 ^0 0/3 6:11 ^1 0/0 12:17 ^2 0/0 18:23 ^3 0/0 24:29 ^4 0/0 30:35 ^5 0/0 36:41 ^0 0/0 42:47 ^1 0/0 48:53 ^2 0/0 54:59 ^3 0/0 60:65 ^4 0/0 66:71 ^5 0/0 72:77 ^0 0/0 78:83 ^1 0/0 84:89 ^2 0/0 90:95 ^3 0/0 96:101 ^4 0/0 102:107 ^5 0/0 108:113 ^0 0/0 114:119 ^1 0/0 120:125 ^2 0/0 126:127 ^3
+c=-226 g=-226 s=1 jfq=-5701 j=72c7 nfqs=88/nfqsng=0(88) fqlh=0 oqlen=0
+0/1 .>. 0:127 ^0
+0/3 .>. 0:35 ^0 0/0 .>. 36:71 ^1 0/0 .>. 72:107 ^2 0/0 .>. 108:127 ^3
+0/3f .>. 0:5 ^0 0/3 .>. 6:11 ^1 0/0 .>. 12:17 ^2 0/0 .>. 18:23 ^3 0/0 .>. 24:29 ^4 0/0 .>. 30:35 ^5 0/0 .>. 36:41 ^0 0/0 .>. 42:47 ^1 0/0 .>. 48:53 ^2 0/0 .>. 54:59 ^3 0/0 .>. 60:65 ^4 0/0 .>. 66:71 ^5 0/0 .>. 72:77 ^0 0/0 .>. 78:83 ^1 0/0 .>. 84:89 ^2 0/0 .>. 90:95 ^3 0/0 .>. 96:101 ^4 0/0 .>. 102:107 ^5 0/0 .>. 108:113 ^0 0/0 .>. 114:119 ^1 0/0 .>. 120:125 ^2 0/0 .>. 126:127 ^3
-This is once again split into "rcu" and "rcu_bh" portions. The fields are
-as follows:
+This is once again split into "rcu_sched" and "rcu_bh" portions,
+and CONFIG_TREE_PREEMPT_RCU kernels will again have an additional
+"rcu_preempt" section. The fields are as follows:
o "c" is exactly the same as "completed" under rcu/rcugp.
@@ -372,6 +201,11 @@ o "fqlh" is the number of calls to force_quiescent_state() that
exited immediately (without even being counted in nfqs above)
due to contention on ->fqslock.
+o "oqlen" is the number of callbacks on the "orphan" callback
+ list. RCU callbacks are placed on this list by CPUs going
+ offline, and are "adopted" either by the CPU helping the outgoing
+ CPU or by the next rcu_barrier*() call, whichever comes first.
+
o Each element of the form "1/1 0:127 ^0" represents one struct
rcu_node. Each line represents one level of the hierarchy, from
root to leaves. It is best to think of the rcu_data structures
@@ -379,7 +213,7 @@ o Each element of the form "1/1 0:127 ^0" represents one struct
might be either one, two, or three levels of rcu_node structures,
depending on the relationship between CONFIG_RCU_FANOUT and
CONFIG_NR_CPUS.
-
+
o The numbers separated by the "/" are the qsmask followed
by the qsmaskinit. The qsmask will have one bit
set for each entity in the next lower level that
@@ -389,10 +223,19 @@ o Each element of the form "1/1 0:127 ^0" represents one struct
The value of qsmaskinit is assigned to that of qsmask
at the beginning of each grace period.
- For example, for "rcu", the qsmask of the first entry
- of the lowest level is 0x14, meaning that we are still
- waiting for CPUs 2 and 4 to check in for the current
- grace period.
+ For example, for "rcu_sched", the qsmask of the first
+ entry of the lowest level is 0x14, meaning that we
+ are still waiting for CPUs 2 and 4 to check in for the
+ current grace period.
+
+ o The characters separated by the ">" indicate the state
+ of the blocked-tasks lists. A "T" preceding the ">"
+ indicates that at least one task blocked in an RCU
+ read-side critical section blocks the current grace
+ period, while a "." preceding the ">" indicates otherwise.
+ The character following the ">" indicates similarly for
+ the next grace period. A "T" should appear in this
+ field only for rcu-preempt.
o The numbers separated by the ":" are the range of CPUs
served by this struct rcu_node. This can be helpful
@@ -431,8 +274,9 @@ rcu_bh:
6 np=120834 qsp=9902 cbr=0 cng=0 gpc=6 gps=3 nf=2 nn=110921
7 np=144888 qsp=26336 cbr=0 cng=0 gpc=8 gps=2 nf=0 nn=118542
-As always, this is once again split into "rcu" and "rcu_bh" portions.
-The fields are as follows:
+As always, this is once again split into "rcu_sched" and "rcu_bh"
+portions, with CONFIG_TREE_PREEMPT_RCU kernels having an additional
+"rcu_preempt" section. The fields are as follows:
o "np" is the number of times that __rcu_pending() has been invoked
for the corresponding flavor of RCU.
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index e41a7fecf0d..d542ca243b8 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -830,7 +830,7 @@ sched: Critical sections Grace period Barrier
SRCU: Critical sections Grace period Barrier
srcu_read_lock synchronize_srcu N/A
- srcu_read_unlock
+ srcu_read_unlock synchronize_srcu_expedited
SRCU: Initialization/cleanup
init_srcu_struct
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 6d527ee82b2..d5b387669da 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -139,10 +139,34 @@ static inline void account_system_vtime(struct task_struct *tsk)
#endif
#if defined(CONFIG_NO_HZ)
+#if defined(CONFIG_TINY_RCU)
+extern void rcu_enter_nohz(void);
+extern void rcu_exit_nohz(void);
+
+static inline void rcu_irq_enter(void)
+{
+ rcu_exit_nohz();
+}
+
+static inline void rcu_irq_exit(void)
+{
+ rcu_enter_nohz();
+}
+
+static inline void rcu_nmi_enter(void)
+{
+}
+
+static inline void rcu_nmi_exit(void)
+{
+}
+
+#else
extern void rcu_irq_enter(void);
extern void rcu_irq_exit(void);
extern void rcu_nmi_enter(void);
extern void rcu_nmi_exit(void);
+#endif
#else
# define rcu_irq_enter() do { } while (0)
# define rcu_irq_exit() do { } while (0)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 3ebd0b7bcb0..24440f4bf47 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -52,11 +52,6 @@ struct rcu_head {
};
/* Exported common interfaces */
-#ifdef CONFIG_TREE_PREEMPT_RCU
-extern void synchronize_rcu(void);
-#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
-#define synchronize_rcu synchronize_sched
-#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
extern void synchronize_rcu_bh(void);
extern void synchronize_sched(void);
extern void rcu_barrier(void);
@@ -67,12 +62,11 @@ extern int sched_expedited_torture_stats(char *page);
/* Internal to kernel */
extern void rcu_init(void);
-extern void rcu_scheduler_starting(void);
-extern int rcu_needs_cpu(int cpu);
-extern int rcu_scheduler_active;
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
#include <linux/rcutree.h>
+#elif defined(CONFIG_TINY_RCU)
+#include <linux/rcutiny.h>
#else
#error "Unknown RCU implementation specified to kernel configuration"
#endif
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
new file mode 100644
index 00000000000..c4ba9a78721
--- /dev/null
+++ b/include/linux/rcutiny.h
@@ -0,0 +1,104 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU
+ */
+#ifndef __LINUX_TINY_H
+#define __LINUX_TINY_H
+
+#include <linux/cache.h>
+
+void rcu_sched_qs(int cpu);
+void rcu_bh_qs(int cpu);
+
+#define __rcu_read_lock() preempt_disable()
+#define __rcu_read_unlock() preempt_enable()
+#define __rcu_read_lock_bh() local_bh_disable()
+#define __rcu_read_unlock_bh() local_bh_enable()
+#define call_rcu_sched call_rcu
+
+#define rcu_init_sched() do { } while (0)
+extern void rcu_check_callbacks(int cpu, int user);
+
+static inline int rcu_needs_cpu(int cpu)
+{
+ return 0;
+}
+
+/*
+ * Return the number of grace periods.
+ */
+static inline long rcu_batches_completed(void)
+{
+ return 0;
+}
+
+/*
+ * Return the number of bottom-half grace periods.
+ */
+static inline long rcu_batches_completed_bh(void)
+{
+ return 0;
+}
+
+extern int rcu_expedited_torture_stats(char *page);
+
+#define synchronize_rcu synchronize_sched
+
+static inline void synchronize_rcu_expedited(void)
+{
+ synchronize_sched();
+}
+
+static inline void synchronize_rcu_bh_expedited(void)
+{
+ synchronize_sched();
+}
+
+struct notifier_block;
+
+#ifdef CONFIG_NO_HZ
+
+extern void rcu_enter_nohz(void);
+extern void rcu_exit_nohz(void);
+
+#else /* #ifdef CONFIG_NO_HZ */
+
+static inline void rcu_enter_nohz(void)
+{
+}
+
+static inline void rcu_exit_nohz(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_NO_HZ */
+
+static inline void rcu_scheduler_starting(void)
+{
+}
+
+static inline void exit_rcu(void)
+{
+}
+
+#endif /* __LINUX_RCUTINY_H */
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 9642c6bcb39..c93eee5911b 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -34,15 +34,15 @@ struct notifier_block;
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
-extern int rcu_cpu_notify(struct notifier_block *self,
- unsigned long action, void *hcpu);
extern int rcu_needs_cpu(int cpu);
+extern void rcu_scheduler_starting(void);
extern int rcu_expedited_torture_stats(char *page);
#ifdef CONFIG_TREE_PREEMPT_RCU
extern void __rcu_read_lock(void);
extern void __rcu_read_unlock(void);
+extern void synchronize_rcu(void);
extern void exit_rcu(void);
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
@@ -57,7 +57,7 @@ static inline void __rcu_read_unlock(void)
preempt_enable();
}
-#define __synchronize_sched() synchronize_rcu()
+#define synchronize_rcu synchronize_sched
static inline void exit_rcu(void)
{
@@ -83,7 +83,6 @@ static inline void synchronize_rcu_bh_expedited(void)
synchronize_sched_expedited();
}
-extern void __rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern long rcu_batches_completed(void);
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index aca0eee5393..4765d97dcaf 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -48,6 +48,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp);
int srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
void synchronize_srcu(struct srcu_struct *sp);
+void synchronize_srcu_expedited(struct srcu_struct *sp);
long srcu_batches_completed(struct srcu_struct *sp);
#endif
diff --git a/init/Kconfig b/init/Kconfig
index 2e9a1457132..9ee77829475 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -334,6 +334,15 @@ config TREE_PREEMPT_RCU
is also required. It also scales down nicely to
smaller systems.
+config TINY_RCU
+ bool "UP-only small-memory-footprint RCU"
+ depends on !SMP
+ help
+ This option selects the RCU implementation that is
+ designed for UP systems from which real-time response
+ is not required. This option greatly reduces the
+ memory footprint of RCU.
+
endchoice
config RCU_TRACE
diff --git a/kernel/Makefile b/kernel/Makefile
index d7c13d249b2..dcf6789bf54 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
obj-$(CONFIG_TREE_RCU) += rcutree.o
obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o
obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o
+obj-$(CONFIG_TINY_RCU) += rcutiny.o
obj-$(CONFIG_RELAY) += relay.o
obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 400183346ad..9b7fd472387 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -44,7 +44,6 @@
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/module.h>
-#include <linux/kernel_stat.h>
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
@@ -53,8 +52,6 @@ struct lockdep_map rcu_lock_map =
EXPORT_SYMBOL_GPL(rcu_lock_map);
#endif
-int rcu_scheduler_active __read_mostly;
-
/*
* Awaken the corresponding synchronize_rcu() instance now that a
* grace period has elapsed.
@@ -66,122 +63,3 @@ void wakeme_after_rcu(struct rcu_head *head)
rcu = container_of(head, struct rcu_synchronize, head);
complete(&rcu->completion);
}
-
-#ifdef CONFIG_TREE_PREEMPT_RCU
-
-/**
- * synchronize_rcu - wait until a grace period has elapsed.
- *
- * Control will return to the caller some time after a full grace
- * period has elapsed, in other words after all currently executing RCU
- * read-side critical sections have completed. RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
- * and may be nested.
- */
-void synchronize_rcu(void)
-{
- struct rcu_synchronize rcu;
-
- if (!rcu_scheduler_active)
- return;
-
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- call_rcu(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu);
-
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
-
-/**
- * synchronize_sched - wait until an rcu-sched grace period has elapsed.
- *
- * Control will return to the caller some time after a full rcu-sched
- * grace period has elapsed, in other words after all currently executing
- * rcu-sched read-side critical sections have completed. These read-side
- * critical sections are delimited by rcu_read_lock_sched() and
- * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
- * local_irq_disable(), and so on may be used in place of
- * rcu_read_lock_sched().
- *
- * This means that all preempt_disable code sequences, including NMI and
- * hardware-interrupt handlers, in progress on entry will have completed
- * before this primitive returns. However, this does not guarantee that
- * softirq handlers will have completed, since in some kernels, these
- * handlers can run in process context, and can block.
- *
- * This primitive provides the guarantees made by the (now removed)
- * synchronize_kernel() API. In contrast, synchronize_rcu() only
- * guarantees that rcu_read_lock() sections will have completed.
- * In "classic RCU", these two guarantees happen to be one and
- * the same, but can differ in realtime RCU implementations.
- */
-void synchronize_sched(void)
-{
- struct rcu_synchronize rcu;
-
- if (rcu_blocking_is_gp())
- return;
-
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- call_rcu_sched(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
-}
-EXPORT_SYMBOL_GPL(synchronize_sched);
-
-/**
- * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
- *
- * Control will return to the caller some time after a full rcu_bh grace
- * period has elapsed, in other words after all currently executing rcu_bh
- * read-side critical sections have completed. RCU read-side critical
- * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
- * and may be nested.
- */
-void synchronize_rcu_bh(void)
-{
- struct rcu_synchronize rcu;
-
- if (rcu_blocking_is_gp())
- return;
-
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- call_rcu_bh(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
-
-static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
- unsigned long action, void *hcpu)
-{
- return rcu_cpu_notify(self, action, hcpu);
-}
-
-void __init rcu_init(void)
-{
- int i;
-
- __rcu_init();
- cpu_notifier(rcu_barrier_cpu_hotplug, 0);
-
- /*
- * We don't need protection against CPU-hotplug here because
- * this is called early in boot, before either interrupts
- * or the scheduler are operational.
- */
- for_each_online_cpu(i)
- rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);
-}
-
-void rcu_scheduler_starting(void)
-{
- WARN_ON(num_online_cpus() != 1);
- WARN_ON(nr_context_switches() > 0);
- rcu_scheduler_active = 1;
-}
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
new file mode 100644
index 00000000000..9f6d9ff2572
--- /dev/null
+++ b/kernel/rcutiny.c
@@ -0,0 +1,282 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU
+ */
+#include <linux/moduleparam.h>
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/time.h>
+#include <linux/cpu.h>
+
+/* Global control variables for rcupdate callback mechanism. */
+struct rcu_ctrlblk {
+ struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
+ struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
+ struct rcu_head **curtail; /* ->next pointer of last CB. */
+};
+
+/* Definition for rcupdate control block. */
+static struct rcu_ctrlblk rcu_ctrlblk = {
+ .donetail = &rcu_ctrlblk.rcucblist,
+ .curtail = &rcu_ctrlblk.rcucblist,
+};
+
+static struct rcu_ctrlblk rcu_bh_ctrlblk = {
+ .donetail = &rcu_bh_ctrlblk.rcucblist,
+ .curtail = &rcu_bh_ctrlblk.rcucblist,
+};
+
+#ifdef CONFIG_NO_HZ
+
+static long rcu_dynticks_nesting = 1;
+
+/*
+ * Enter dynticks-idle mode, which is an extended quiescent state
+ * if we have fully entered that mode (i.e., if the new value of
+ * dynticks_nesting is zero).
+ */
+void rcu_enter_nohz(void)
+{
+ if (--rcu_dynticks_nesting == 0)
+ rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+}
+
+/*
+ * Exit dynticks-idle mode, so that we are no longer in an extended
+ * quiescent state.
+ */
+void rcu_exit_nohz(void)
+{
+ rcu_dynticks_nesting++;
+}
+
+#endif /* #ifdef CONFIG_NO_HZ */
+
+/*
+ * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
+ * Also disable irqs to avoid confusion due to interrupt handlers
+ * invoking call_rcu().
+ */
+static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ if (rcp->rcucblist != NULL &&
+ rcp->donetail != rcp->curtail) {
+ rcp->donetail = rcp->curtail;
+ local_irq_restore(flags);
+ return 1;
+ }
+ local_irq_restore(flags);
+
+ return 0;
+}
+
+/*
+ * Record an rcu quiescent state. And an rcu_bh quiescent state while we
+ * are at it, given that any rcu quiescent state is also an rcu_bh
+ * quiescent state. Use "+" instead of "||" to defeat short circuiting.
+ */
+void rcu_sched_qs(int cpu)
+{
+ if (rcu_qsctr_help(&rcu_ctrlblk) + rcu_qsctr_help(&rcu_bh_ctrlblk))
+ raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Record an rcu_bh quiescent state.
+ */
+void rcu_bh_qs(int cpu)
+{
+ if (rcu_qsctr_help(&rcu_bh_ctrlblk))
+ raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Check to see if the scheduling-clock interrupt came from an extended
+ * quiescent state, and, if so, tell RCU about it.
+ */
+void rcu_check_callbacks(int cpu, int user)
+{
+ if (user ||
+ (idle_cpu(cpu) &&
+ !in_softirq() &&
+ hardirq_count() <= (1 << HARDIRQ_SHIFT)))
+ rcu_sched_qs(cpu);
+ else if (!in_softirq())
+ rcu_bh_qs(cpu);
+}
+
+/*
+ * Helper function for rcu_process_callbacks() that operates on the
+ * specified rcu_ctrlkblk structure.
+ */
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+{
+ struct rcu_head *next, *list;
+ unsigned long flags;
+
+ /* If no RCU callbacks ready to invoke, just return. */
+ if (&rcp->rcucblist == rcp->donetail)
+ return;
+
+ /* Move the ready-to-invoke callbacks to a local list. */
+ local_irq_save(flags);
+ list = rcp->rcucblist;
+ rcp->rcucblist = *rcp->donetail;
+ *rcp->donetail = NULL;
+ if (rcp->curtail == rcp->donetail)
+ rcp->curtail = &rcp->rcucblist;
+ rcp->donetail = &rcp->rcucblist;
+ local_irq_restore(flags);
+
+ /* Invoke the callbacks on the local list. */
+ while (list) {
+ next = list->next;
+ prefetch(next);
+ list->func(list);
+ list = next;
+ }
+}
+
+/*
+ * Invoke any callbacks whose grace period has completed.
+ */
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+ __rcu_process_callbacks(&rcu_ctrlblk);
+ __rcu_process_callbacks(&rcu_bh_ctrlblk);
+}
+
+/*
+ * Wait for a grace period to elapse. But it is illegal to invoke
+ * synchronize_sched() from within an RCU read-side critical section.
+ * Therefore, any legal call to synchronize_sched() is a quiescent
+ * state, and so on a UP system, synchronize_sched() need do nothing.
+ * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the
+ * benefits of doing might_sleep() to reduce latency.)
+ *
+ * Cool, huh? (Due to Josh Triplett.)
+ *
+ * But we want to make this a static inline later.
+ */
+void synchronize_sched(void)
+{
+ cond_resched();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+void synchronize_rcu_bh(void)
+{
+ synchronize_sched();
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+
+/*
+ * Helper function for call_rcu() and call_rcu_bh().
+ */
+static void __call_rcu(struct rcu_head *head,
+ void (*func)(struct rcu_head *rcu),
+ struct rcu_ctrlblk *rcp)
+{
+ unsigned long flags;
+
+ head->func = func;
+ head->next = NULL;
+
+ local_irq_save(flags);
+ *rcp->curtail = head;
+ rcp->curtail = &head->next;
+ local_irq_restore(flags);
+}
+
+/*
+ * Post an RCU callback to be invoked after the end of an RCU grace
+ * period. But since we have but one CPU, that would be after any
+ * quiescent state.
+ */
+void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+ __call_rcu(head, func, &rcu_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Post an RCU bottom-half callback to be invoked after any subsequent
+ * quiescent state.
+ */
+void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+ __call_rcu(head, func, &rcu_bh_ctrlblk);
+}
+EXPORT_SYMBOL_GPL(call_rcu_bh);
+
+void rcu_barrier(void)
+{
+ struct rcu_synchronize rcu;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
+void rcu_barrier_bh(void)
+{
+ struct rcu_synchronize rcu;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu_bh(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_bh);
+
+void rcu_barrier_sched(void)
+{
+ struct rcu_synchronize rcu;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu_sched(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+
+void __init rcu_init(void)
+{
+ open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+}
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 697c0a0229d..a621a67ef4e 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -327,6 +327,11 @@ rcu_torture_cb(struct rcu_head *p)
cur_ops->deferred_free(rp);
}
+static int rcu_no_completed(void)
+{
+ return 0;
+}
+
static void rcu_torture_deferred_free(struct rcu_torture *p)
{
call_rcu(&p->rtort_rcu, rcu_torture_cb);
@@ -388,6 +393,21 @@ static struct rcu_torture_ops rcu_sync_ops = {
.name = "rcu_sync"
};
+static struct rcu_torture_ops rcu_expedited_ops = {
+ .init = rcu_sync_torture_init,
+ .cleanup = NULL,
+ .readlock = rcu_torture_read_lock,
+ .read_delay = rcu_read_delay, /* just reuse rcu's version. */
+ .readunlock = rcu_torture_read_unlock,
+ .completed = rcu_no_completed,
+ .deferred_free = rcu_sync_torture_deferred_free,
+ .sync = synchronize_rcu_expedited,
+ .cb_barrier = NULL,
+ .stats = NULL,
+ .irq_capable = 1,
+ .name = "rcu_expedited"
+};
+
/*
* Definitions for rcu_bh torture testing.
*/
@@ -547,6 +567,25 @@ static struct rcu_torture_ops srcu_ops = {
.name = "srcu"
};
+static void srcu_torture_synchronize_expedited(void)
+{
+ synchronize_srcu_expedited(&srcu_ctl);
+}
+
+static struct rcu_torture_ops srcu_expedited_ops = {
+ .init = srcu_torture_init,
+ .cleanup = srcu_torture_cleanup,
+ .readlock = srcu_torture_read_lock,
+ .read_delay = srcu_read_delay,
+ .readunlock = srcu_torture_read_unlock,
+ .completed = srcu_torture_completed,
+ .deferred_free = rcu_sync_torture_deferred_free,
+ .sync = srcu_torture_synchronize_expedited,
+ .cb_barrier = NULL,
+ .stats = srcu_torture_stats,
+ .name = "srcu_expedited"
+};
+
/*
* Definitions for sched torture testing.
*/
@@ -562,11 +601,6 @@ static void sched_torture_read_unlock(int idx)
preempt_enable();
}
-static int sched_torture_completed(void)
-{
- return 0;
-}
-
static void rcu_sched_torture_deferred_free(struct rcu_torture *p)
{
call_rcu_sched(&p->rtort_rcu, rcu_torture_cb);
@@ -583,7 +617,7 @@ static struct rcu_torture_ops sched_ops = {
.readlock = sched_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = sched_torture_read_unlock,
- .completed = sched_torture_completed,
+ .completed = rcu_no_completed,
.deferred_free = rcu_sched_torture_deferred_free,
.sync = sched_torture_synchronize,
.cb_barrier = rcu_barrier_sched,
@@ -592,13 +626,13 @@ static struct rcu_torture_ops sched_ops = {
.name = "sched"
};
-static struct rcu_torture_ops sched_ops_sync = {
+static struct rcu_torture_ops sched_sync_ops = {
.init = rcu_sync_torture_init,
.cleanup = NULL,
.readlock = sched_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = sched_torture_read_unlock,
- .completed = sched_torture_completed,
+ .completed = rcu_no_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = sched_torture_synchronize,
.cb_barrier = NULL,
@@ -612,7 +646,7 @@ static struct rcu_torture_ops sched_expedited_ops = {
.readlock = sched_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = sched_torture_read_unlock,
- .completed = sched_torture_completed,
+ .completed = rcu_no_completed,
.deferred_free = rcu_sync_torture_deferred_free,
.sync = synchronize_sched_expedited,
.cb_barrier = NULL,
@@ -1097,9 +1131,10 @@ rcu_torture_init(void)
int cpu;
int firsterr = 0;
static struct rcu_torture_ops *torture_ops[] =
- { &rcu_ops, &rcu_sync_ops, &rcu_bh_ops, &rcu_bh_sync_ops,
- &sched_expedited_ops,
- &srcu_ops, &sched_ops, &sched_ops_sync, };
+ { &rcu_ops, &rcu_sync_ops, &rcu_expedited_ops,
+ &rcu_bh_ops, &rcu_bh_sync_ops,
+ &srcu_ops, &srcu_expedited_ops,
+ &sched_ops, &sched_sync_ops, &sched_expedited_ops, };
mutex_lock(&fullstop_mutex);
@@ -1110,8 +1145,12 @@ rcu_torture_init(void)
break;
}
if (i == ARRAY_SIZE(torture_ops)) {
- printk(KERN_ALERT "rcutorture: invalid torture type: \"%s\"\n",
+ printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
torture_type);
+ printk(KERN_ALERT "rcu-torture types:");
+ for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
+ printk(KERN_ALERT " %s", torture_ops[i]->name);
+ printk(KERN_ALERT "\n");
mutex_unlock(&fullstop_mutex);
return -EINVAL;
}
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f3077c0ab18..53ae9598f79 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -46,18 +46,22 @@
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/time.h>
+#include <linux/kernel_stat.h>
#include "rcutree.h"
/* Data structures. */
+static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
+
#define RCU_STATE_INITIALIZER(name) { \
.level = { &name.node[0] }, \
.levelcnt = { \
NUM_RCU_LVL_0, /* root of hierarchy. */ \
NUM_RCU_LVL_1, \
NUM_RCU_LVL_2, \
- NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \
+ NUM_RCU_LVL_3, \
+ NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
}, \
.signaled = RCU_GP_IDLE, \
.gpnum = -300, \
@@ -77,6 +81,8 @@ DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
+static int rcu_scheduler_active __read_mostly;
+
/*
* Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
@@ -98,7 +104,7 @@ void rcu_sched_qs(int cpu)
struct rcu_data *rdp;
rdp = &per_cpu(rcu_sched_data, cpu);
- rdp->passed_quiesc_completed = rdp->completed;
+ rdp->passed_quiesc_completed = rdp->gpnum - 1;
barrier();
rdp->passed_quiesc = 1;
rcu_preempt_note_context_switch(cpu);
@@ -109,7 +115,7 @@ void rcu_bh_qs(int cpu)
struct rcu_data *rdp;
rdp = &per_cpu(rcu_bh_data, cpu);
- rdp->passed_quiesc_completed = rdp->completed;
+ rdp->passed_quiesc_completed = rdp->gpnum - 1;
barrier();
rdp->passed_quiesc = 1;
}
@@ -335,28 +341,9 @@ void rcu_irq_exit(void)
set_need_resched();
}
-/*
- * Record the specified "completed" value, which is later used to validate
- * dynticks counter manipulations. Specify "rsp->completed - 1" to
- * unconditionally invalidate any future dynticks manipulations (which is
- * useful at the beginning of a grace period).
- */
-static void dyntick_record_completed(struct rcu_state *rsp, long comp)
-{
- rsp->dynticks_completed = comp;
-}
-
#ifdef CONFIG_SMP
/*
- * Recall the previously recorded value of the completion for dynticks.
- */
-static long dyntick_recall_completed(struct rcu_state *rsp)
-{
- return rsp->dynticks_completed;
-}
-
-/*
* Snapshot the specified CPU's dynticks counter so that we can later
* credit them with an implicit quiescent state. Return 1 if this CPU
* is in dynticks idle mode, which is an extended quiescent state.
@@ -419,24 +406,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
#else /* #ifdef CONFIG_NO_HZ */
-static void dyntick_record_completed(struct rcu_state *rsp, long comp)
-{
-}
-
#ifdef CONFIG_SMP
-/*
- * If there are no dynticks, then the only way that a CPU can passively
- * be in a quiescent state is to be offline. Unlike dynticks idle, which
- * is a point in time during the prior (already finished) grace period,
- * an offline CPU is always in a quiescent state, and thus can be
- * unconditionally applied. So just return the current value of completed.
- */
-static long dyntick_recall_completed(struct rcu_state *rsp)
-{
- return rsp->completed;
-}
-
static int dyntick_save_progress_counter(struct rcu_data *rdp)
{
return 0;
@@ -553,13 +524,33 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
/*
* Update CPU-local rcu_data state to record the newly noticed grace period.
* This is used both when we started the grace period and when we notice
- * that someone else started the grace period.
+ * that someone else started the grace period. The caller must hold the
+ * ->lock of the leaf rcu_node structure corresponding to the current CPU,
+ * and must have irqs disabled.
*/
+static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
+{
+ if (rdp->gpnum != rnp->gpnum) {
+ rdp->qs_pending = 1;
+ rdp->passed_quiesc = 0;
+ rdp->gpnum = rnp->gpnum;
+ }
+}
+
static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
{
- rdp->qs_pending = 1;
- rdp->passed_quiesc = 0;
- rdp->gpnum = rsp->gpnum;
+ unsigned long flags;
+ struct rcu_node *rnp;
+
+ local_irq_save(flags);
+ rnp = rdp->mynode;
+ if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */
+ !spin_trylock(&rnp->lock)) { /* irqs already off, retry later. */
+ local_irq_restore(flags);
+ return;
+ }
+ __note_new_gpnum(rsp, rnp, rdp);
+ spin_unlock_irqrestore(&rnp->lock, flags);
}
/*
@@ -583,6 +574,79 @@ check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
}
/*
+ * Advance this CPU's callbacks, but only if the current grace period
+ * has ended. This may be called only from the CPU to whom the rdp
+ * belongs. In addition, the corresponding leaf rcu_node structure's
+ * ->lock must be held by the caller, with irqs disabled.
+ */
+static void
+__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
+{
+ /* Did another grace period end? */
+ if (rdp->completed != rnp->completed) {
+
+ /* Advance callbacks. No harm if list empty. */
+ rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
+ rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
+ rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+ /* Remember that we saw this grace-period completion. */
+ rdp->completed = rnp->completed;
+ }
+}
+
+/*
+ * Advance this CPU's callbacks, but only if the current grace period
+ * has ended. This may be called only from the CPU to whom the rdp
+ * belongs.
+ */
+static void
+rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ unsigned long flags;
+ struct rcu_node *rnp;
+
+ local_irq_save(flags);
+ rnp = rdp->mynode;
+ if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
+ !spin_trylock(&rnp->lock)) { /* irqs already off, retry later. */
+ local_irq_restore(flags);
+ return;
+ }
+ __rcu_process_gp_end(rsp, rnp, rdp);
+ spin_unlock_irqrestore(&rnp->lock, flags);
+}
+
+/*
+ * Do per-CPU grace-period initialization for running CPU. The caller
+ * must hold the lock of the leaf rcu_node structure corresponding to
+ * this CPU.
+ */
+static void
+rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
+{
+ /* Prior grace period ended, so advance callbacks for current CPU. */
+ __rcu_process_gp_end(rsp, rnp, rdp);
+
+ /*
+ * Because this CPU just now started the new grace period, we know
+ * that all of its callbacks will be covered by this upcoming grace
+ * period, even the ones that were registered arbitrarily recently.
+ * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
+ *
+ * Other CPUs cannot be sure exactly when the grace period started.
+ * Therefore, their recently registered callbacks must pass through
+ * an additional RCU_NEXT_READY stage, so that they will be handled
+ * by the next RCU grace period.
+ */
+ rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+ rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+ /* Set state so that this CPU will detect the next quiescent state. */
+ __note_new_gpnum(rsp, rnp, rdp);
+}
+
+/*
* Start a new RCU grace period if warranted, re-initializing the hierarchy
* in preparation for detecting the next grace period. The caller must hold
* the root node's ->lock, which is released before return. Hard irqs must
@@ -596,7 +660,23 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
struct rcu_node *rnp = rcu_get_root(rsp);
if (!cpu_needs_another_gp(rsp, rdp)) {
- spin_unlock_irqrestore(&rnp->lock, flags);
+ if (rnp->completed == rsp->completed) {
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+ spin_unlock(&rnp->lock); /* irqs remain disabled. */
+
+ /*
+ * Propagate new ->completed value to rcu_node structures
+ * so that other CPUs don't have to wait until the start
+ * of the next grace period to process their callbacks.
+ */
+ rcu_for_each_node_breadth_first(rsp, rnp) {
+ spin_lock(&rnp->lock); /* irqs already disabled. */
+ rnp->completed = rsp->completed;
+ spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ }
+ local_irq_restore(flags);
return;
}
@@ -606,29 +686,15 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
record_gp_stall_check_time(rsp);
- dyntick_record_completed(rsp, rsp->completed - 1);
- note_new_gpnum(rsp, rdp);
-
- /*
- * Because this CPU just now started the new grace period, we know
- * that all of its callbacks will be covered by this upcoming grace
- * period, even the ones that were registered arbitrarily recently.
- * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
- *
- * Other CPUs cannot be sure exactly when the grace period started.
- * Therefore, their recently registered callbacks must pass through
- * an additional RCU_NEXT_READY stage, so that they will be handled
- * by the next RCU grace period.
- */
- rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
- rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
/* Special-case the common single-level case. */
if (NUM_RCU_NODES == 1) {
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
rnp->gpnum = rsp->gpnum;
+ rnp->completed = rsp->completed;
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
+ rcu_start_gp_per_cpu(rsp, rnp, rdp);
spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
@@ -661,6 +727,9 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
rnp->gpnum = rsp->gpnum;
+ rnp->completed = rsp->completed;
+ if (rnp == rdp->mynode)
+ rcu_start_gp_per_cpu(rsp, rnp, rdp);
spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
@@ -672,58 +741,32 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
}
/*
- * Advance this CPU's callbacks, but only if the current grace period
- * has ended. This may be called only from the CPU to whom the rdp
- * belongs.
+ * Report a full set of quiescent states to the specified rcu_state
+ * data structure. This involves cleaning up after the prior grace
+ * period and letting rcu_start_gp() start up the next grace period
+ * if one is needed. Note that the caller must hold rnp->lock, as
+ * required by rcu_start_gp(), which will release it.
*/
-static void
-rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
-{
- long completed_snap;
- unsigned long flags;
-
- local_irq_save(flags);
- completed_snap = ACCESS_ONCE(rsp->completed); /* outside of lock. */
-
- /* Did another grace period end? */
- if (rdp->completed != completed_snap) {
-
- /* Advance callbacks. No harm if list empty. */
- rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
- rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
- rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
-
- /* Remember that we saw this grace-period completion. */
- rdp->completed = completed_snap;
- }
- local_irq_restore(flags);
-}
-
-/*
- * Clean up after the prior grace period and let rcu_start_gp() start up
- * the next grace period if one is needed. Note that the caller must
- * hold rnp->lock, as required by rcu_start_gp(), which will release it.
- */
-static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags)
+static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
__releases(rcu_get_root(rsp)->lock)
{
WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
rsp->completed = rsp->gpnum;
rsp->signaled = RCU_GP_IDLE;
- rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]);
rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
}
/*
- * Similar to cpu_quiet(), for which it is a helper function. Allows
- * a group of CPUs to be quieted at one go, though all the CPUs in the
- * group must be represented by the same leaf rcu_node structure.
- * That structure's lock must be held upon entry, and it is released
- * before return.
+ * Similar to rcu_report_qs_rdp(), for which it is a helper function.
+ * Allows quiescent states for a group of CPUs to be reported at one go
+ * to the specified rcu_node structure, though all the CPUs in the group
+ * must be represented by the same rcu_node structure (which need not be
+ * a leaf rcu_node structure, though it often will be). That structure's
+ * lock must be held upon entry, and it is released before return.
*/
static void
-cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
- unsigned long flags)
+rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
+ struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
{
struct rcu_node *rnp_c;
@@ -759,21 +802,23 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
/*
* Get here if we are the last CPU to pass through a quiescent
- * state for this grace period. Invoke cpu_quiet_msk_finish()
+ * state for this grace period. Invoke rcu_report_qs_rsp()
* to clean up and start the next grace period if one is needed.
*/
- cpu_quiet_msk_finish(rsp, flags); /* releases rnp->lock. */
+ rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
}
/*
- * Record a quiescent state for the specified CPU, which must either be
- * the current CPU. The lastcomp argument is used to make sure we are
- * still in the grace period of interest. We don't want to end the current
- * grace period based on quiescent states detected in an earlier grace
- * period!
+ * Record a quiescent state for the specified CPU to that CPU's rcu_data
+ * structure. This must be either called from the specified CPU, or
+ * called when the specified CPU is known to be offline (and when it is
+ * also known that no other CPU is concurrently trying to help the offline
+ * CPU). The lastcomp argument is used to make sure we are still in the
+ * grace period of interest. We don't want to end the current grace period
+ * based on quiescent states detected in an earlier grace period!
*/
static void
-cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
+rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
{
unsigned long flags;
unsigned long mask;
@@ -781,15 +826,15 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
rnp = rdp->mynode;
spin_lock_irqsave(&rnp->lock, flags);
- if (lastcomp != ACCESS_ONCE(rsp->completed)) {
+ if (lastcomp != rnp->completed) {
/*
* Someone beat us to it for this grace period, so leave.
* The race with GP start is resolved by the fact that we
* hold the leaf rcu_node lock, so that the per-CPU bits
* cannot yet be initialized -- so we would simply find our
- * CPU's bit already cleared in cpu_quiet_msk() if this race
- * occurred.
+ * CPU's bit already cleared in rcu_report_qs_rnp() if this
+ * race occurred.
*/
rdp->passed_quiesc = 0; /* try again later! */
spin_unlock_irqrestore(&rnp->lock, flags);
@@ -807,7 +852,7 @@ cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
*/
rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
- cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */
+ rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
}
}
@@ -838,8 +883,11 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
if (!rdp->passed_quiesc)
return;
- /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */
- cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed);
+ /*
+ * Tell RCU we are done (but rcu_report_qs_rdp() will be the
+ * judge of that).
+ */
+ rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed);
}
#ifdef CONFIG_HOTPLUG_CPU
@@ -899,8 +947,8 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp)
static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
- long lastcomp;
unsigned long mask;
+ int need_report = 0;
struct rcu_data *rdp = rsp->rda[cpu];
struct rcu_node *rnp;
@@ -914,30 +962,32 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
spin_lock(&rnp->lock); /* irqs already disabled. */
rnp->qsmaskinit &= ~mask;
if (rnp->qsmaskinit != 0) {
- spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ if (rnp != rdp->mynode)
+ spin_unlock(&rnp->lock); /* irqs remain disabled. */
break;
}
-
- /*
- * If there was a task blocking the current grace period,
- * and if all CPUs have checked in, we need to propagate
- * the quiescent state up the rcu_node hierarchy. But that
- * is inconvenient at the moment due to deadlock issues if
- * this should end the current grace period. So set the
- * offlined CPU's bit in ->qsmask in order to force the
- * next force_quiescent_state() invocation to clean up this
- * mess in a deadlock-free manner.
- */
- if (rcu_preempt_offline_tasks(rsp, rnp, rdp) && !rnp->qsmask)
- rnp->qsmask |= mask;
-
+ if (rnp == rdp->mynode)
+ need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
+ else
+ spin_unlock(&rnp->lock); /* irqs remain disabled. */
mask = rnp->grpmask;
- spin_unlock(&rnp->lock); /* irqs remain disabled. */
rnp = rnp->parent;
} while (rnp != NULL);
- lastcomp = rsp->completed;
- spin_unlock_irqrestore(&rsp->onofflock, flags);
+ /*
+ * We still hold the leaf rcu_node structure lock here, and
+ * irqs are still disabled. The reason for this subterfuge is
+ * because invoking rcu_report_unblock_qs_rnp() with ->onofflock
+ * held leads to deadlock.
+ */
+ spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
+ rnp = rdp->mynode;
+ if (need_report & RCU_OFL_TASKS_NORM_GP)
+ rcu_report_unblock_qs_rnp(rnp, flags);
+ else
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ if (need_report & RCU_OFL_TASKS_EXP_GP)
+ rcu_report_exp_rnp(rsp, rnp);
rcu_adopt_orphan_cbs(rsp);
}
@@ -1109,7 +1159,7 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
rcu_for_each_leaf_node(rsp, rnp) {
mask = 0;
spin_lock_irqsave(&rnp->lock, flags);
- if (rsp->completed != lastcomp) {
+ if (rnp->completed != lastcomp) {
spin_unlock_irqrestore(&rnp->lock, flags);
return 1;
}
@@ -1123,10 +1173,10 @@ static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu]))
mask |= bit;
}
- if (mask != 0 && rsp->completed == lastcomp) {
+ if (mask != 0 && rnp->completed == lastcomp) {
- /* cpu_quiet_msk() releases rnp->lock. */
- cpu_quiet_msk(mask, rsp, rnp, flags);
+ /* rcu_report_qs_rnp() releases rnp->lock. */
+ rcu_report_qs_rnp(mask, rsp, rnp, flags);
continue;
}
spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1144,6 +1194,7 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
long lastcomp;
struct rcu_node *rnp = rcu_get_root(rsp);
u8 signaled;
+ u8 forcenow;
if (!rcu_gp_in_progress(rsp))
return; /* No grace period in progress, nothing to force. */
@@ -1156,10 +1207,10 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
goto unlock_ret; /* no emergency and done recently. */
rsp->n_force_qs++;
spin_lock(&rnp->lock);
- lastcomp = rsp->completed;
+ lastcomp = rsp->gpnum - 1;
signaled = rsp->signaled;
rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
- if (lastcomp == rsp->gpnum) {
+ if(!rcu_gp_in_progress(rsp)) {
rsp->n_force_qs_ngp++;
spin_unlock(&rnp->lock);
goto unlock_ret; /* no GP in progress, time updated. */
@@ -1180,21 +1231,29 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
if (rcu_process_dyntick(rsp, lastcomp,
dyntick_save_progress_counter))
goto unlock_ret;
+ /* fall into next case. */
+
+ case RCU_SAVE_COMPLETED:
/* Update state, record completion counter. */
+ forcenow = 0;
spin_lock(&rnp->lock);
- if (lastcomp == rsp->completed &&
- rsp->signaled == RCU_SAVE_DYNTICK) {
+ if (lastcomp + 1 == rsp->gpnum &&
+ lastcomp == rsp->completed &&
+ rsp->signaled == signaled) {
rsp->signaled = RCU_FORCE_QS;
- dyntick_record_completed(rsp, lastcomp);
+ rsp->completed_fqs = lastcomp;
+ forcenow = signaled == RCU_SAVE_COMPLETED;
}
spin_unlock(&rnp->lock);
- break;
+ if (!forcenow)
+ break;
+ /* fall into next case. */
case RCU_FORCE_QS:
/* Check dyntick-idle state, send IPI to laggarts. */
- if (rcu_process_dyntick(rsp, dyntick_recall_completed(rsp),
+ if (rcu_process_dyntick(rsp, rsp->completed_fqs,
rcu_implicit_dynticks_qs))
goto unlock_ret;
@@ -1351,6 +1410,68 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
}
EXPORT_SYMBOL_GPL(call_rcu_bh);
+/**
+ * synchronize_sched - wait until an rcu-sched grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu-sched
+ * grace period has elapsed, in other words after all currently executing
+ * rcu-sched read-side critical sections have completed. These read-side
+ * critical sections are delimited by rcu_read_lock_sched() and
+ * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
+ * local_irq_disable(), and so on may be used in place of
+ * rcu_read_lock_sched().
+ *
+ * This means that all preempt_disable code sequences, including NMI and
+ * hardware-interrupt handlers, in progress on entry will have completed
+ * before this primitive returns. However, this does not guarantee that
+ * softirq handlers will have completed, since in some kernels, these
+ * handlers can run in process context, and can block.
+ *
+ * This primitive provides the guarantees made by the (now removed)
+ * synchronize_kernel() API. In contrast, synchronize_rcu() only
+ * guarantees that rcu_read_lock() sections will have completed.
+ * In "classic RCU", these two guarantees happen to be one and
+ * the same, but can differ in realtime RCU implementations.
+ */
+void synchronize_sched(void)
+{
+ struct rcu_synchronize rcu;
+
+ if (rcu_blocking_is_gp())
+ return;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu_sched(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(synchronize_sched);
+
+/**
+ * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu_bh grace
+ * period has elapsed, in other words after all currently executing rcu_bh
+ * read-side critical sections have completed. RCU read-side critical
+ * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
+ * and may be nested.
+ */
+void synchronize_rcu_bh(void)
+{
+ struct rcu_synchronize rcu;
+
+ if (rcu_blocking_is_gp())
+ return;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu_bh(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+
/*
* Check to see if there is any immediate RCU-related work to be done
* by the current CPU, for the specified type of RCU, returning 1 if so.
@@ -1360,6 +1481,8 @@ EXPORT_SYMBOL_GPL(call_rcu_bh);
*/
static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
{
+ struct rcu_node *rnp = rdp->mynode;
+
rdp->n_rcu_pending++;
/* Check for CPU stalls, if enabled. */
@@ -1384,13 +1507,13 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
}
/* Has another RCU grace period completed? */
- if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */
+ if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
rdp->n_rp_gp_completed++;
return 1;
}
/* Has a new RCU grace period started? */
- if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */
+ if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
rdp->n_rp_gp_started++;
return 1;
}
@@ -1433,6 +1556,21 @@ int rcu_needs_cpu(int cpu)
rcu_preempt_needs_cpu(cpu);
}
+/*
+ * This function is invoked towards the end of the scheduler's initialization
+ * process. Before this is called, the idle task might contain
+ * RCU read-side critical sections (during which time, this idle
+ * task is booting the system). After this function is called, the
+ * idle tasks are prohibited from containing RCU read-side critical
+ * sections.
+ */
+void rcu_scheduler_starting(void)
+{
+ WARN_ON(num_online_cpus() != 1);
+ WARN_ON(nr_context_switches() > 0);
+ rcu_scheduler_active = 1;
+}
+
static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
@@ -1544,21 +1682,16 @@ static void __cpuinit
rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
{
unsigned long flags;
- long lastcomp;
unsigned long mask;
struct rcu_data *rdp = rsp->rda[cpu];
struct rcu_node *rnp = rcu_get_root(rsp);
/* Set up local state, ensuring consistent view of global state. */
spin_lock_irqsave(&rnp->lock, flags);
- lastcomp = rsp->completed;
- rdp->completed = lastcomp;
- rdp->gpnum = lastcomp;
rdp->passed_quiesc = 0; /* We could be racing with new GP, */
rdp->qs_pending = 1; /* so set up to respond to current GP. */
rdp->beenonline = 1; /* We have now been online. */
rdp->preemptable = preemptable;
- rdp->passed_quiesc_completed = lastcomp - 1;
rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = rsp->n_force_qs;
rdp->blimit = blimit;
@@ -1580,6 +1713,11 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable)
spin_lock(&rnp->lock); /* irqs already disabled. */
rnp->qsmaskinit |= mask;
mask = rnp->grpmask;
+ if (rnp == rdp->mynode) {
+ rdp->gpnum = rnp->completed; /* if GP in progress... */
+ rdp->completed = rnp->completed;
+ rdp->passed_quiesc_completed = rnp->completed - 1;
+ }
spin_unlock(&rnp->lock); /* irqs already disabled. */
rnp = rnp->parent;
} while (rnp != NULL && !(rnp->qsmaskinit & mask));
@@ -1597,8 +1735,8 @@ static void __cpuinit rcu_online_cpu(int cpu)
/*
* Handle CPU online/offline notification events.
*/
-int __cpuinit rcu_cpu_notify(struct notifier_block *self,
- unsigned long action, void *hcpu)
+static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
{
long cpu = (long)hcpu;
@@ -1685,8 +1823,8 @@ static void __init rcu_init_one(struct rcu_state *rsp)
cpustride *= rsp->levelspread[i];
rnp = rsp->level[i];
for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
- if (rnp != rcu_get_root(rsp))
- spin_lock_init(&rnp->lock);
+ spin_lock_init(&rnp->lock);
+ lockdep_set_class(&rnp->lock, &rcu_node_class[i]);
rnp->gpnum = 0;
rnp->qsmask = 0;
rnp->qsmaskinit = 0;
@@ -1707,9 +1845,10 @@ static void __init rcu_init_one(struct rcu_state *rsp)
rnp->level = i;
INIT_LIST_HEAD(&rnp->blocked_tasks[0]);
INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
+ INIT_LIST_HEAD(&rnp->blocked_tasks[2]);
+ INIT_LIST_HEAD(&rnp->blocked_tasks[3]);
}
}
- spin_lock_init(&rcu_get_root(rsp)->lock);
}
/*
@@ -1735,16 +1874,30 @@ do { \
} \
} while (0)
-void __init __rcu_init(void)
+void __init rcu_init(void)
{
+ int i;
+
rcu_bootup_announce();
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+#if NUM_RCU_LVL_4 != 0
+ printk(KERN_INFO "Experimental four-level hierarchy is enabled.\n");
+#endif /* #if NUM_RCU_LVL_4 != 0 */
RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data);
RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data);
__rcu_init_preempt();
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+
+ /*
+ * We don't need protection against CPU-hotplug here because
+ * this is called early in boot, before either interrupts
+ * or the scheduler are operational.
+ */
+ cpu_notifier(rcu_cpu_notify, 0);
+ for_each_online_cpu(i)
+ rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)i);
}
#include "rcutree_plugin.h"
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 1899023b096..d2a0046f63b 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -34,10 +34,11 @@
* In practice, this has not been tested, so there is probably some
* bug somewhere.
*/
-#define MAX_RCU_LVLS 3
+#define MAX_RCU_LVLS 4
#define RCU_FANOUT (CONFIG_RCU_FANOUT)
#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT)
#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT)
+#define RCU_FANOUT_FOURTH (RCU_FANOUT_CUBE * RCU_FANOUT)
#if NR_CPUS <= RCU_FANOUT
# define NUM_RCU_LVLS 1
@@ -45,23 +46,33 @@
# define NUM_RCU_LVL_1 (NR_CPUS)
# define NUM_RCU_LVL_2 0
# define NUM_RCU_LVL_3 0
+# define NUM_RCU_LVL_4 0
#elif NR_CPUS <= RCU_FANOUT_SQ
# define NUM_RCU_LVLS 2
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)
# define NUM_RCU_LVL_2 (NR_CPUS)
# define NUM_RCU_LVL_3 0
+# define NUM_RCU_LVL_4 0
#elif NR_CPUS <= RCU_FANOUT_CUBE
# define NUM_RCU_LVLS 3
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ)
# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)
# define NUM_RCU_LVL_3 NR_CPUS
+# define NUM_RCU_LVL_4 0
+#elif NR_CPUS <= RCU_FANOUT_FOURTH
+# define NUM_RCU_LVLS 4
+# define NUM_RCU_LVL_0 1
+# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_CUBE)
+# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ)
+# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)
+# define NUM_RCU_LVL_4 NR_CPUS
#else
# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
#endif /* #if (NR_CPUS) <= RCU_FANOUT */
-#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
+#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4)
#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
/*
@@ -84,14 +95,21 @@ struct rcu_node {
long gpnum; /* Current grace period for this node. */
/* This will either be equal to or one */
/* behind the root rcu_node's gpnum. */
+ long completed; /* Last grace period completed for this node. */
+ /* This will either be equal to or one */
+ /* behind the root rcu_node's gpnum. */
unsigned long qsmask; /* CPUs or groups that need to switch in */
/* order for current grace period to proceed.*/
/* In leaf rcu_node, each bit corresponds to */
/* an rcu_data structure, otherwise, each */
/* bit corresponds to a child rcu_node */
/* structure. */
+ unsigned long expmask; /* Groups that have ->blocked_tasks[] */
+ /* elements that need to drain to allow the */
+ /* current expedited grace period to */
+ /* complete (only for TREE_PREEMPT_RCU). */
unsigned long qsmaskinit;
- /* Per-GP initialization for qsmask. */
+ /* Per-GP initial value for qsmask & expmask. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
/* Only one bit will be set in this mask. */
int grplo; /* lowest-numbered CPU or group here. */
@@ -99,7 +117,7 @@ struct rcu_node {
u8 grpnum; /* CPU/group number for next level up. */
u8 level; /* root is at level 0. */
struct rcu_node *parent;
- struct list_head blocked_tasks[2];
+ struct list_head blocked_tasks[4];
/* Tasks blocked in RCU read-side critsect. */
/* Grace period number (->gpnum) x blocked */
/* by tasks on the (x & 0x1) element of the */
@@ -114,6 +132,21 @@ struct rcu_node {
for ((rnp) = &(rsp)->node[0]; \
(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
+/*
+ * Do a breadth-first scan of the non-leaf rcu_node structures for the
+ * specified rcu_state structure. Note that if there is a singleton
+ * rcu_node tree with but one rcu_node structure, this loop is a no-op.
+ */
+#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
+ for ((rnp) = &(rsp)->node[0]; \
+ (rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++)
+
+/*
+ * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
+ * structure. Note that if there is a singleton rcu_node tree with but
+ * one rcu_node structure, this loop -will- visit the rcu_node structure.
+ * It is still a leaf node, even if it is also the root node.
+ */
#define rcu_for_each_leaf_node(rsp, rnp) \
for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \
(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
@@ -204,11 +237,12 @@ struct rcu_data {
#define RCU_GP_IDLE 0 /* No grace period in progress. */
#define RCU_GP_INIT 1 /* Grace period being initialized. */
#define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */
-#define RCU_FORCE_QS 3 /* Need to force quiescent state. */
+#define RCU_SAVE_COMPLETED 3 /* Need to save rsp->completed. */
+#define RCU_FORCE_QS 4 /* Need to force quiescent state. */
#ifdef CONFIG_NO_HZ
#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
#else /* #ifdef CONFIG_NO_HZ */
-#define RCU_SIGNAL_INIT RCU_FORCE_QS
+#define RCU_SIGNAL_INIT RCU_SAVE_COMPLETED
#endif /* #else #ifdef CONFIG_NO_HZ */
#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
@@ -246,7 +280,7 @@ struct rcu_state {
long gpnum; /* Current gp number. */
long completed; /* # of last completed gp. */
- /* End of fields guarded by root rcu_node's lock. */
+ /* End of fields guarded by root rcu_node's lock. */
spinlock_t onofflock; /* exclude on/offline and */
/* starting new GP. Also */
@@ -260,6 +294,8 @@ struct rcu_state {
long orphan_qlen; /* Number of orphaned cbs. */
spinlock_t fqslock; /* Only one task forcing */
/* quiescent states. */
+ long completed_fqs; /* Value of completed @ snap. */
+ /* Protected by fqslock. */
unsigned long jiffies_force_qs; /* Time at which to invoke */
/* force_quiescent_state(). */
unsigned long n_force_qs; /* Number of calls to */
@@ -274,11 +310,15 @@ struct rcu_state {
unsigned long jiffies_stall; /* Time at which to check */
/* for CPU stalls. */
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
-#ifdef CONFIG_NO_HZ
- long dynticks_completed; /* Value of completed @ snap. */
-#endif /* #ifdef CONFIG_NO_HZ */
};
+/* Return values for rcu_preempt_offline_tasks(). */
+
+#define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */
+ /* GP were moved to root. */
+#define RCU_OFL_TASKS_EXP_GP 0x2 /* Tasks blocking expedited */
+ /* GP were moved to root. */
+
#ifdef RCU_TREE_NONCORE
/*
@@ -298,10 +338,14 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
#else /* #ifdef RCU_TREE_NONCORE */
/* Forward declarations for rcutree_plugin.h */
-static inline void rcu_bootup_announce(void);
+static void rcu_bootup_announce(void);
long rcu_batches_completed(void);
static void rcu_preempt_note_context_switch(int cpu);
static int rcu_preempted_readers(struct rcu_node *rnp);
+#ifdef CONFIG_HOTPLUG_CPU
+static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
+ unsigned long flags);
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
static void rcu_print_task_stall(struct rcu_node *rnp);
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
@@ -315,6 +359,9 @@ static void rcu_preempt_offline_cpu(int cpu);
static void rcu_preempt_check_callbacks(int cpu);
static void rcu_preempt_process_callbacks(void);
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
+static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp);
+#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
static int rcu_preempt_pending(int cpu);
static int rcu_preempt_needs_cpu(int cpu);
static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index ef2a58c2b9d..37fbccdf41d 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -24,16 +24,19 @@
* Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
+#include <linux/delay.h>
#ifdef CONFIG_TREE_PREEMPT_RCU
struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state);
DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
+static int rcu_preempted_readers_exp(struct rcu_node *rnp);
+
/*
* Tell them what RCU they are running.
*/
-static inline void rcu_bootup_announce(void)
+static void __init rcu_bootup_announce(void)
{
printk(KERN_INFO
"Experimental preemptable hierarchical RCU implementation.\n");
@@ -67,7 +70,7 @@ EXPORT_SYMBOL_GPL(rcu_batches_completed);
static void rcu_preempt_qs(int cpu)
{
struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu);
- rdp->passed_quiesc_completed = rdp->completed;
+ rdp->passed_quiesc_completed = rdp->gpnum - 1;
barrier();
rdp->passed_quiesc = 1;
}
@@ -157,14 +160,58 @@ EXPORT_SYMBOL_GPL(__rcu_read_lock);
*/
static int rcu_preempted_readers(struct rcu_node *rnp)
{
- return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
+ int phase = rnp->gpnum & 0x1;
+
+ return !list_empty(&rnp->blocked_tasks[phase]) ||
+ !list_empty(&rnp->blocked_tasks[phase + 2]);
+}
+
+/*
+ * Record a quiescent state for all tasks that were previously queued
+ * on the specified rcu_node structure and that were blocking the current
+ * RCU grace period. The caller must hold the specified rnp->lock with
+ * irqs disabled, and this lock is released upon return, but irqs remain
+ * disabled.
+ */
+static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
+ __releases(rnp->lock)
+{
+ unsigned long mask;
+ struct rcu_node *rnp_p;
+
+ if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) {
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return; /* Still need more quiescent states! */
+ }
+
+ rnp_p = rnp->parent;
+ if (rnp_p == NULL) {
+ /*
+ * Either there is only one rcu_node in the tree,
+ * or tasks were kicked up to root rcu_node due to
+ * CPUs going offline.
+ */
+ rcu_report_qs_rsp(&rcu_preempt_state, flags);
+ return;
+ }
+
+ /* Report up the rest of the hierarchy. */
+ mask = rnp->grpmask;
+ spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ spin_lock(&rnp_p->lock); /* irqs already disabled. */
+ rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags);
}
+/*
+ * Handle special cases during rcu_read_unlock(), such as needing to
+ * notify RCU core processing or task having blocked during the RCU
+ * read-side critical section.
+ */
static void rcu_read_unlock_special(struct task_struct *t)
{
int empty;
+ int empty_exp;
unsigned long flags;
- unsigned long mask;
struct rcu_node *rnp;
int special;
@@ -207,36 +254,30 @@ static void rcu_read_unlock_special(struct task_struct *t)
spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
empty = !rcu_preempted_readers(rnp);
+ empty_exp = !rcu_preempted_readers_exp(rnp);
+ smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
list_del_init(&t->rcu_node_entry);
t->rcu_blocked_node = NULL;
/*
* If this was the last task on the current list, and if
* we aren't waiting on any CPUs, report the quiescent state.
- * Note that both cpu_quiet_msk_finish() and cpu_quiet_msk()
- * drop rnp->lock and restore irq.
+ * Note that rcu_report_unblock_qs_rnp() releases rnp->lock.
*/
- if (!empty && rnp->qsmask == 0 &&
- !rcu_preempted_readers(rnp)) {
- struct rcu_node *rnp_p;
-
- if (rnp->parent == NULL) {
- /* Only one rcu_node in the tree. */
- cpu_quiet_msk_finish(&rcu_preempt_state, flags);
- return;
- }
- /* Report up the rest of the hierarchy. */
- mask = rnp->grpmask;
+ if (empty)
spin_unlock_irqrestore(&rnp->lock, flags);
- rnp_p = rnp->parent;
- spin_lock_irqsave(&rnp_p->lock, flags);
- WARN_ON_ONCE(rnp->qsmask);
- cpu_quiet_msk(mask, &rcu_preempt_state, rnp_p, flags);
- return;
- }
- spin_unlock(&rnp->lock);
+ else
+ rcu_report_unblock_qs_rnp(rnp, flags);
+
+ /*
+ * If this was the last task on the expedited lists,
+ * then we need to report up the rcu_node hierarchy.
+ */
+ if (!empty_exp && !rcu_preempted_readers_exp(rnp))
+ rcu_report_exp_rnp(&rcu_preempt_state, rnp);
+ } else {
+ local_irq_restore(flags);
}
- local_irq_restore(flags);
}
/*
@@ -303,6 +344,8 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
* rcu_node. The reason for not just moving them to the immediate
* parent is to remove the need for rcu_read_unlock_special() to
* make more than two attempts to acquire the target rcu_node's lock.
+ * Returns true if there were tasks blocking the current RCU grace
+ * period.
*
* Returns 1 if there was previously a task blocking the current grace
* period on the specified rcu_node structure.
@@ -316,7 +359,7 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
int i;
struct list_head *lp;
struct list_head *lp_root;
- int retval = rcu_preempted_readers(rnp);
+ int retval = 0;
struct rcu_node *rnp_root = rcu_get_root(rsp);
struct task_struct *tp;
@@ -326,7 +369,9 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
}
WARN_ON_ONCE(rnp != rdp->mynode &&
(!list_empty(&rnp->blocked_tasks[0]) ||
- !list_empty(&rnp->blocked_tasks[1])));
+ !list_empty(&rnp->blocked_tasks[1]) ||
+ !list_empty(&rnp->blocked_tasks[2]) ||
+ !list_empty(&rnp->blocked_tasks[3])));
/*
* Move tasks up to root rcu_node. Rely on the fact that the
@@ -334,7 +379,11 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
* rcu_nodes in terms of gp_num value. This fact allows us to
* move the blocked_tasks[] array directly, element by element.
*/
- for (i = 0; i < 2; i++) {
+ if (rcu_preempted_readers(rnp))
+ retval |= RCU_OFL_TASKS_NORM_GP;
+ if (rcu_preempted_readers_exp(rnp))
+ retval |= RCU_OFL_TASKS_EXP_GP;
+ for (i = 0; i < 4; i++) {
lp = &rnp->blocked_tasks[i];
lp_root = &rnp_root->blocked_tasks[i];
while (!list_empty(lp)) {
@@ -346,7 +395,6 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
spin_unlock(&rnp_root->lock); /* irqs remain disabled */
}
}
-
return retval;
}
@@ -398,14 +446,183 @@ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
}
EXPORT_SYMBOL_GPL(call_rcu);
+/**
+ * synchronize_rcu - wait until a grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full grace
+ * period has elapsed, in other words after all currently executing RCU
+ * read-side critical sections have completed. RCU read-side critical
+ * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
+ * and may be nested.
+ */
+void synchronize_rcu(void)
+{
+ struct rcu_synchronize rcu;
+
+ if (!rcu_scheduler_active)
+ return;
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu);
+
+static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
+static long sync_rcu_preempt_exp_count;
+static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);
+
/*
- * Wait for an rcu-preempt grace period. We are supposed to expedite the
- * grace period, but this is the crude slow compatability hack, so just
- * invoke synchronize_rcu().
+ * Return non-zero if there are any tasks in RCU read-side critical
+ * sections blocking the current preemptible-RCU expedited grace period.
+ * If there is no preemptible-RCU expedited grace period currently in
+ * progress, returns zero unconditionally.
+ */
+static int rcu_preempted_readers_exp(struct rcu_node *rnp)
+{
+ return !list_empty(&rnp->blocked_tasks[2]) ||
+ !list_empty(&rnp->blocked_tasks[3]);
+}
+
+/*
+ * return non-zero if there is no RCU expedited grace period in progress
+ * for the specified rcu_node structure, in other words, if all CPUs and
+ * tasks covered by the specified rcu_node structure have done their bit
+ * for the current expedited grace period. Works only for preemptible
+ * RCU -- other RCU implementation use other means.
+ *
+ * Caller must hold sync_rcu_preempt_exp_mutex.
+ */
+static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
+{
+ return !rcu_preempted_readers_exp(rnp) &&
+ ACCESS_ONCE(rnp->expmask) == 0;
+}
+
+/*
+ * Report the exit from RCU read-side critical section for the last task
+ * that queued itself during or before the current expedited preemptible-RCU
+ * grace period. This event is reported either to the rcu_node structure on
+ * which the task was queued or to one of that rcu_node structure's ancestors,
+ * recursively up the tree. (Calm down, calm down, we do the recursion
+ * iteratively!)
+ *
+ * Caller must hold sync_rcu_preempt_exp_mutex.
+ */
+static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
+{
+ unsigned long flags;
+ unsigned long mask;
+
+ spin_lock_irqsave(&rnp->lock, flags);
+ for (;;) {
+ if (!sync_rcu_preempt_exp_done(rnp))
+ break;
+ if (rnp->parent == NULL) {
+ wake_up(&sync_rcu_preempt_exp_wq);
+ break;
+ }
+ mask = rnp->grpmask;
+ spin_unlock(&rnp->lock); /* irqs remain disabled */
+ rnp = rnp->parent;
+ spin_lock(&rnp->lock); /* irqs already disabled */
+ rnp->expmask &= ~mask;
+ }
+ spin_unlock_irqrestore(&rnp->lock, flags);
+}
+
+/*
+ * Snapshot the tasks blocking the newly started preemptible-RCU expedited
+ * grace period for the specified rcu_node structure. If there are no such
+ * tasks, report it up the rcu_node hierarchy.
+ *
+ * Caller must hold sync_rcu_preempt_exp_mutex and rsp->onofflock.
+ */
+static void
+sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
+{
+ int must_wait;
+
+ spin_lock(&rnp->lock); /* irqs already disabled */
+ list_splice_init(&rnp->blocked_tasks[0], &rnp->blocked_tasks[2]);
+ list_splice_init(&rnp->blocked_tasks[1], &rnp->blocked_tasks[3]);
+ must_wait = rcu_preempted_readers_exp(rnp);
+ spin_unlock(&rnp->lock); /* irqs remain disabled */
+ if (!must_wait)
+ rcu_report_exp_rnp(rsp, rnp);
+}
+
+/*
+ * Wait for an rcu-preempt grace period, but expedite it. The basic idea
+ * is to invoke synchronize_sched_expedited() to push all the tasks to
+ * the ->blocked_tasks[] lists, move all entries from the first set of
+ * ->blocked_tasks[] lists to the second set, and finally wait for this
+ * second set to drain.
*/
void synchronize_rcu_expedited(void)
{
- synchronize_rcu();
+ unsigned long flags;
+ struct rcu_node *rnp;
+ struct rcu_state *rsp = &rcu_preempt_state;
+ long snap;
+ int trycount = 0;
+
+ smp_mb(); /* Caller's modifications seen first by other CPUs. */
+ snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1;
+ smp_mb(); /* Above access cannot bleed into critical section. */
+
+ /*
+ * Acquire lock, falling back to synchronize_rcu() if too many
+ * lock-acquisition failures. Of course, if someone does the
+ * expedited grace period for us, just leave.
+ */
+ while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) {
+ if (trycount++ < 10)
+ udelay(trycount * num_online_cpus());
+ else {
+ synchronize_rcu();
+ return;
+ }
+ if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0)
+ goto mb_ret; /* Others did our work for us. */
+ }
+ if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0)
+ goto unlock_mb_ret; /* Others did our work for us. */
+
+ /* force all RCU readers onto blocked_tasks[]. */
+ synchronize_sched_expedited();
+
+ spin_lock_irqsave(&rsp->onofflock, flags);
+
+ /* Initialize ->expmask for all non-leaf rcu_node structures. */
+ rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) {
+ spin_lock(&rnp->lock); /* irqs already disabled. */
+ rnp->expmask = rnp->qsmaskinit;
+ spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ }
+
+ /* Snapshot current state of ->blocked_tasks[] lists. */
+ rcu_for_each_leaf_node(rsp, rnp)
+ sync_rcu_preempt_exp_init(rsp, rnp);
+ if (NUM_RCU_NODES > 1)
+ sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp));
+
+ spin_unlock_irqrestore(&rsp->onofflock, flags);
+
+ /* Wait for snapshotted ->blocked_tasks[] lists to drain. */
+ rnp = rcu_get_root(rsp);
+ wait_event(sync_rcu_preempt_exp_wq,
+ sync_rcu_preempt_exp_done(rnp));
+
+ /* Clean up and exit. */
+ smp_mb(); /* ensure expedited GP seen before counter increment. */
+ ACCESS_ONCE(sync_rcu_preempt_exp_count)++;
+unlock_mb_ret:
+ mutex_unlock(&sync_rcu_preempt_exp_mutex);
+mb_ret:
+ smp_mb(); /* ensure subsequent action seen after grace period. */
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
@@ -481,7 +698,7 @@ void exit_rcu(void)
/*
* Tell them what RCU they are running.
*/
-static inline void rcu_bootup_announce(void)
+static void __init rcu_bootup_announce(void)
{
printk(KERN_INFO "Hierarchical RCU implementation.\n");
}
@@ -512,6 +729,16 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
return 0;
}
+#ifdef CONFIG_HOTPLUG_CPU
+
+/* Because preemptible RCU does not exist, no quieting of tasks. */
+static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
+{
+ spin_unlock_irqrestore(&rnp->lock, flags);
+}
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
/*
@@ -594,6 +821,20 @@ void synchronize_rcu_expedited(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Because preemptable RCU does not exist, there is never any need to
+ * report on tasks preempted in RCU read-side critical sections during
+ * expedited RCU grace periods.
+ */
+static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp)
+{
+ return;
+}
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+
/*
* Because preemptable RCU does not exist, it never has any work to do.
*/
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index 4b31c779e62..9d2c88423b3 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -155,12 +155,15 @@ static const struct file_operations rcudata_csv_fops = {
static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
{
+ long gpnum;
int level = 0;
+ int phase;
struct rcu_node *rnp;
+ gpnum = rsp->gpnum;
seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x "
"nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld\n",
- rsp->completed, rsp->gpnum, rsp->signaled,
+ rsp->completed, gpnum, rsp->signaled,
(long)(rsp->jiffies_force_qs - jiffies),
(int)(jiffies & 0xffff),
rsp->n_force_qs, rsp->n_force_qs_ngp,
@@ -171,8 +174,13 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
seq_puts(m, "\n");
level = rnp->level;
}
- seq_printf(m, "%lx/%lx %d:%d ^%d ",
+ phase = gpnum & 0x1;
+ seq_printf(m, "%lx/%lx %c%c>%c%c %d:%d ^%d ",
rnp->qsmask, rnp->qsmaskinit,
+ "T."[list_empty(&rnp->blocked_tasks[phase])],
+ "E."[list_empty(&rnp->blocked_tasks[phase + 2])],
+ "T."[list_empty(&rnp->blocked_tasks[!phase])],
+ "E."[list_empty(&rnp->blocked_tasks[!phase + 2])],
rnp->grplo, rnp->grphi, rnp->grpnum);
}
seq_puts(m, "\n");
diff --git a/kernel/sched.c b/kernel/sched.c
index ec0af1fcb19..6ae2739b8f1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -10901,6 +10901,7 @@ void synchronize_sched_expedited(void)
spin_unlock_irqrestore(&rq->lock, flags);
}
rcu_expedited_state = RCU_EXPEDITED_STATE_IDLE;
+ synchronize_sched_expedited_count++;
mutex_unlock(&rcu_sched_expedited_mutex);
put_online_cpus();
if (need_full_sync)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index f8749e5216e..21939d9e830 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -302,9 +302,9 @@ void irq_exit(void)
if (!in_interrupt() && local_softirq_pending())
invoke_softirq();
+ rcu_irq_exit();
#ifdef CONFIG_NO_HZ
/* Make sure that timer wheel updates are propagated */
- rcu_irq_exit();
if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
tick_nohz_stop_sched_tick(0);
#endif
diff --git a/kernel/srcu.c b/kernel/srcu.c
index b0aeeaf22ce..818d7d9aa03 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -49,6 +49,7 @@ int init_srcu_struct(struct srcu_struct *sp)
sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
return (sp->per_cpu_ref ? 0 : -ENOMEM);
}
+EXPORT_SYMBOL_GPL(init_srcu_struct);
/*
* srcu_readers_active_idx -- returns approximate number of readers
@@ -97,6 +98,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp)
free_percpu(sp->per_cpu_ref);
sp->per_cpu_ref = NULL;
}
+EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
/**
* srcu_read_lock - register a new reader for an SRCU-protected structure.
@@ -118,6 +120,7 @@ int srcu_read_lock(struct srcu_struct *sp)
preempt_enable();
return idx;
}
+EXPORT_SYMBOL_GPL(srcu_read_lock);
/**
* srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
@@ -136,22 +139,12 @@ void srcu_read_unlock(struct srcu_struct *sp, int idx)
per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
preempt_enable();
}
+EXPORT_SYMBOL_GPL(srcu_read_unlock);
-/**
- * synchronize_srcu - wait for prior SRCU read-side critical-section completion
- * @sp: srcu_struct with which to synchronize.
- *
- * Flip the completed counter, and wait for the old count to drain to zero.
- * As with classic RCU, the updater must use some separate means of
- * synchronizing concurrent updates. Can block; must be called from
- * process context.
- *
- * Note that it is illegal to call synchornize_srcu() from the corresponding
- * SRCU read-side critical section; doing so will result in deadlock.
- * However, it is perfectly legal to call synchronize_srcu() on one
- * srcu_struct from some other srcu_struct's read-side critical section.
+/*
+ * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
*/
-void synchronize_srcu(struct srcu_struct *sp)
+void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
{
int idx;
@@ -173,7 +166,7 @@ void synchronize_srcu(struct srcu_struct *sp)
return;
}
- synchronize_sched(); /* Force memory barrier on all CPUs. */
+ sync_func(); /* Force memory barrier on all CPUs. */
/*
* The preceding synchronize_sched() ensures that any CPU that
@@ -190,7 +183,7 @@ void synchronize_srcu(struct srcu_struct *sp)
idx = sp->completed & 0x1;
sp->completed++;
- synchronize_sched(); /* Force memory barrier on all CPUs. */
+ sync_func(); /* Force memory barrier on all CPUs. */
/*
* At this point, because of the preceding synchronize_sched(),
@@ -203,7 +196,7 @@ void synchronize_srcu(struct srcu_struct *sp)
while (srcu_readers_active_idx(sp, idx))
schedule_timeout_interruptible(1);
- synchronize_sched(); /* Force memory barrier on all CPUs. */
+ sync_func(); /* Force memory barrier on all CPUs. */
/*
* The preceding synchronize_sched() forces all srcu_read_unlock()
@@ -237,6 +230,47 @@ void synchronize_srcu(struct srcu_struct *sp)
}
/**
+ * synchronize_srcu - wait for prior SRCU read-side critical-section completion
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates. Can block; must be called from
+ * process context.
+ *
+ * Note that it is illegal to call synchronize_srcu() from the corresponding
+ * SRCU read-side critical section; doing so will result in deadlock.
+ * However, it is perfectly legal to call synchronize_srcu() on one
+ * srcu_struct from some other srcu_struct's read-side critical section.
+ */
+void synchronize_srcu(struct srcu_struct *sp)
+{
+ __synchronize_srcu(sp, synchronize_sched);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu);
+
+/**
+ * synchronize_srcu_expedited - like synchronize_srcu, but less patient
+ * @sp: srcu_struct with which to synchronize.
+ *
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates. Can block; must be called from
+ * process context.
+ *
+ * Note that it is illegal to call synchronize_srcu_expedited()
+ * from the corresponding SRCU read-side critical section; doing so
+ * will result in deadlock. However, it is perfectly legal to call
+ * synchronize_srcu_expedited() on one srcu_struct from some other
+ * srcu_struct's read-side critical section.
+ */
+void synchronize_srcu_expedited(struct srcu_struct *sp)
+{
+ __synchronize_srcu(sp, synchronize_sched_expedited);
+}
+EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
+
+/**
* srcu_batches_completed - return batches completed.
* @sp: srcu_struct on which to report batch completion.
*
@@ -248,10 +282,4 @@ long srcu_batches_completed(struct srcu_struct *sp)
{
return sp->completed;
}
-
-EXPORT_SYMBOL_GPL(init_srcu_struct);
-EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
-EXPORT_SYMBOL_GPL(srcu_read_lock);
-EXPORT_SYMBOL_GPL(srcu_read_unlock);
-EXPORT_SYMBOL_GPL(synchronize_srcu);
EXPORT_SYMBOL_GPL(srcu_batches_completed);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 234ceb10861..a79c4d0407a 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -750,7 +750,7 @@ config RCU_TORTURE_TEST_RUNNABLE
config RCU_CPU_STALL_DETECTOR
bool "Check for stalled CPUs delaying RCU grace periods"
depends on TREE_RCU || TREE_PREEMPT_RCU
- default n
+ default y
help
This option causes RCU to printk information on which
CPUs are delaying the current grace period, but only when