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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2008-05-12 21:21:05 +0200
committerIngo Molnar <mingo@elte.hu>2008-05-19 10:01:36 +0200
commit4446a36ff8c74ac3b32feb009b651048e129c6af (patch)
tree4ae726073e02281c2de51ed394ba2a812fd55c9b /include/linux/rcupdate.h
parent8b09dee67f484e9b42114b1a1f068e080fd7aa56 (diff)
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rcu: add call_rcu_sched()
Fourth cut of patch to provide the call_rcu_sched(). This is again to synchronize_sched() as call_rcu() is to synchronize_rcu(). Should be fine for experimental and -rt use, but not ready for inclusion. With some luck, I will be able to tell Andrew to come out of hiding on the next round. Passes multi-day rcutorture sessions with concurrent CPU hotplugging. Fixes since the first version include a bug that could result in indefinite blocking (spotted by Gautham Shenoy), better resiliency against CPU-hotplug operations, and other minor fixes. Fixes since the second version include reworking grace-period detection to avoid deadlocks that could happen when running concurrently with CPU hotplug, adding Mathieu's fix to avoid the softlockup messages, as well as Mathieu's fix to allow use earlier in boot. Fixes since the third version include a wrong-CPU bug spotted by Andrew, getting rid of the obsolete synchronize_kernel API that somehow snuck back in, merging spin_unlock() and local_irq_restore() in a few places, commenting the code that checks for quiescent states based on interrupting from user-mode execution or the idle loop, removing some inline attributes, and some code-style changes. Known/suspected shortcomings: o I still do not entirely trust the sleep/wakeup logic. Next step will be to use a private snapshot of the CPU online mask in rcu_sched_grace_period() -- if the CPU wasn't there at the start of the grace period, we don't need to hear from it. And the bit about accounting for changes in online CPUs inside of rcu_sched_grace_period() is ugly anyway. o It might be good for rcu_sched_grace_period() to invoke resched_cpu() when a given CPU wasn't responding quickly, but resched_cpu() is declared static... This patch also fixes a long-standing bug in the earlier preemptable-RCU implementation of synchronize_rcu() that could result in loss of concurrent external changes to a task's CPU affinity mask. I still cannot remember who reported this... Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h22
1 files changed, 22 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index ec2fc5b3264..411969cb524 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -40,6 +40,7 @@
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#include <linux/lockdep.h>
+#include <linux/completion.h>
/**
* struct rcu_head - callback structure for use with RCU
@@ -168,6 +169,27 @@ struct rcu_head {
(p) = (v); \
})
+/* Infrastructure to implement the synchronize_() primitives. */
+
+struct rcu_synchronize {
+ struct rcu_head head;
+ struct completion completion;
+};
+
+extern void wakeme_after_rcu(struct rcu_head *head);
+
+#define synchronize_rcu_xxx(name, func) \
+void name(void) \
+{ \
+ struct rcu_synchronize rcu; \
+ \
+ init_completion(&rcu.completion); \
+ /* Will wake me after RCU finished. */ \
+ func(&rcu.head, wakeme_after_rcu); \
+ /* Wait for it. */ \
+ wait_for_completion(&rcu.completion); \
+}
+
/**
* synchronize_sched - block until all CPUs have exited any non-preemptive
* kernel code sequences.