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authorIngo Molnar <mingo@kernel.org>2019-06-28 19:46:47 +0200
committerIngo Molnar <mingo@kernel.org>2019-06-28 19:46:47 +0200
commit83086d654dd08c0f57381522e6819f421677706e (patch)
treebcb3d6f66916134de1a86c67db8a5829e3885ef3 /kernel
parent556e2f6020bf90f63c5dd65e9a2254be6db3185b (diff)
parentb989ff070574ad8b8621d866de0a8e9a65d42c80 (diff)
downloadtip-83086d654dd08c0f57381522e6819f421677706e.tar.gz
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Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcucore/rcu
Pull rcu/next + tools/memory-model changes from Paul E. McKenney: - RCU flavor consolidation cleanups and optmizations - Documentation updates - Miscellaneous fixes - SRCU updates - RCU-sync flavor consolidation - Torture-test updates - Linux-kernel memory-consistency-model updates, most notably the addition of plain C-language accesses Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup/cgroup.c3
-rw-r--r--kernel/events/uprobes.c4
-rw-r--r--kernel/locking/locktorture.c2
-rw-r--r--kernel/locking/percpu-rwsem.c2
-rw-r--r--kernel/module.c5
-rw-r--r--kernel/rcu/rcu.h5
-rw-r--r--kernel/rcu/rcutorture.c96
-rw-r--r--kernel/rcu/srcutree.c69
-rw-r--r--kernel/rcu/sync.c214
-rw-r--r--kernel/rcu/tree.c164
-rw-r--r--kernel/rcu/tree.h6
-rw-r--r--kernel/rcu/tree_exp.h53
-rw-r--r--kernel/rcu/tree_plugin.h195
-rw-r--r--kernel/rcu/tree_stall.h4
-rw-r--r--kernel/rcu/update.c13
-rw-r--r--kernel/torture.c23
16 files changed, 540 insertions, 318 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index bf9dbffd46b1..cdbeff87fa99 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -101,7 +101,7 @@ static DEFINE_SPINLOCK(cgroup_idr_lock);
*/
static DEFINE_SPINLOCK(cgroup_file_kn_lock);
-struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
+DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
#define cgroup_assert_mutex_or_rcu_locked() \
RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
@@ -5666,7 +5666,6 @@ int __init cgroup_init(void)
int ssid;
BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
- BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem));
BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 78f61bfc6b79..97c367f0a9aa 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -46,7 +46,7 @@ static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ];
#define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
-static struct percpu_rw_semaphore dup_mmap_sem;
+DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem);
/* Have a copy of original instruction */
#define UPROBE_COPY_INSN 0
@@ -2302,7 +2302,5 @@ void __init uprobes_init(void)
for (i = 0; i < UPROBES_HASH_SZ; i++)
mutex_init(&uprobes_mmap_mutex[i]);
- BUG_ON(percpu_init_rwsem(&dup_mmap_sem));
-
BUG_ON(register_die_notifier(&uprobe_exception_nb));
}
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 80a463d31a8d..c513031cd7e3 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -975,7 +975,7 @@ static int __init lock_torture_init(void)
goto unwind;
}
if (stutter > 0) {
- firsterr = torture_stutter_init(stutter);
+ firsterr = torture_stutter_init(stutter, stutter);
if (firsterr)
goto unwind;
}
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index b6a9cc62099a..364d38a0c444 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -18,7 +18,7 @@ int __percpu_init_rwsem(struct percpu_rw_semaphore *sem,
return -ENOMEM;
/* ->rw_sem represents the whole percpu_rw_semaphore for lockdep */
- rcu_sync_init(&sem->rss, RCU_SCHED_SYNC);
+ rcu_sync_init(&sem->rss);
__init_rwsem(&sem->rw_sem, name, rwsem_key);
rcuwait_init(&sem->writer);
sem->readers_block = 0;
diff --git a/kernel/module.c b/kernel/module.c
index 80c7c09584cf..a2cee14a83f3 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3083,6 +3083,11 @@ static int find_module_sections(struct module *mod, struct load_info *info)
sizeof(*mod->tracepoints_ptrs),
&mod->num_tracepoints);
#endif
+#ifdef CONFIG_TREE_SRCU
+ mod->srcu_struct_ptrs = section_objs(info, "___srcu_struct_ptrs",
+ sizeof(*mod->srcu_struct_ptrs),
+ &mod->num_srcu_structs);
+#endif
#ifdef CONFIG_BPF_EVENTS
mod->bpf_raw_events = section_objs(info, "__bpf_raw_tp_map",
sizeof(*mod->bpf_raw_events),
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 390aab20115e..5290b01de534 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -446,6 +446,7 @@ void rcu_request_urgent_qs_task(struct task_struct *t);
enum rcutorture_type {
RCU_FLAVOR,
RCU_TASKS_FLAVOR,
+ RCU_TRIVIAL_FLAVOR,
SRCU_FLAVOR,
INVALID_RCU_FLAVOR
};
@@ -479,6 +480,10 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
#endif
#endif
+#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
+long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask);
+#endif
+
#ifdef CONFIG_TINY_SRCU
static inline void srcutorture_get_gp_data(enum rcutorture_type test_type,
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index efaa5b3f4d3f..fce4e7e6f502 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -299,6 +299,7 @@ struct rcu_torture_ops {
int irq_capable;
int can_boost;
int extendables;
+ int slow_gps;
const char *name;
};
@@ -667,9 +668,51 @@ static struct rcu_torture_ops tasks_ops = {
.fqs = NULL,
.stats = NULL,
.irq_capable = 1,
+ .slow_gps = 1,
.name = "tasks"
};
+/*
+ * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
+ * This implementation does not necessarily work well with CPU hotplug.
+ */
+
+static void synchronize_rcu_trivial(void)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu) {
+ rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
+ WARN_ON_ONCE(raw_smp_processor_id() != cpu);
+ }
+}
+
+static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
+{
+ preempt_disable();
+ return 0;
+}
+
+static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
+{
+ preempt_enable();
+}
+
+static struct rcu_torture_ops trivial_ops = {
+ .ttype = RCU_TRIVIAL_FLAVOR,
+ .init = rcu_sync_torture_init,
+ .readlock = rcu_torture_read_lock_trivial,
+ .read_delay = rcu_read_delay, /* just reuse rcu's version. */
+ .readunlock = rcu_torture_read_unlock_trivial,
+ .get_gp_seq = rcu_no_completed,
+ .sync = synchronize_rcu_trivial,
+ .exp_sync = synchronize_rcu_trivial,
+ .fqs = NULL,
+ .stats = NULL,
+ .irq_capable = 1,
+ .name = "trivial"
+};
+
static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
{
if (!cur_ops->gp_diff)
@@ -1010,10 +1053,17 @@ rcu_torture_writer(void *arg)
!rcu_gp_is_normal();
}
rcu_torture_writer_state = RTWS_STUTTER;
- if (stutter_wait("rcu_torture_writer"))
+ if (stutter_wait("rcu_torture_writer") &&
+ !READ_ONCE(rcu_fwd_cb_nodelay) &&
+ !cur_ops->slow_gps &&
+ !torture_must_stop())
for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
- if (list_empty(&rcu_tortures[i].rtort_free))
- WARN_ON_ONCE(1);
+ if (list_empty(&rcu_tortures[i].rtort_free) &&
+ rcu_access_pointer(rcu_torture_current) !=
+ &rcu_tortures[i]) {
+ rcu_ftrace_dump(DUMP_ALL);
+ WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
+ }
} while (!torture_must_stop());
/* Reset expediting back to unexpedited. */
if (expediting > 0)
@@ -1358,8 +1408,9 @@ rcu_torture_stats_print(void)
}
pr_alert("%s%s ", torture_type, TORTURE_FLAG);
- pr_cont("rtc: %p ver: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
+ pr_cont("rtc: %p %s: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
rcu_torture_current,
+ rcu_torture_current ? "ver" : "VER",
rcu_torture_current_version,
list_empty(&rcu_torture_freelist),
atomic_read(&n_rcu_torture_alloc),
@@ -1661,6 +1712,17 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
spin_unlock_irqrestore(&rcu_fwd_lock, flags);
}
+// Give the scheduler a chance, even on nohz_full CPUs.
+static void rcu_torture_fwd_prog_cond_resched(void)
+{
+ if (IS_ENABLED(CONFIG_PREEMPT) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
+ if (need_resched())
+ schedule();
+ } else {
+ cond_resched();
+ }
+}
+
/*
* Free all callbacks on the rcu_fwd_cb_head list, either because the
* test is over or because we hit an OOM event.
@@ -1674,16 +1736,18 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void)
for (;;) {
spin_lock_irqsave(&rcu_fwd_lock, flags);
rfcp = rcu_fwd_cb_head;
- if (!rfcp)
+ if (!rfcp) {
+ spin_unlock_irqrestore(&rcu_fwd_lock, flags);
break;
+ }
rcu_fwd_cb_head = rfcp->rfc_next;
if (!rcu_fwd_cb_head)
rcu_fwd_cb_tail = &rcu_fwd_cb_head;
spin_unlock_irqrestore(&rcu_fwd_lock, flags);
kfree(rfcp);
freed++;
+ rcu_torture_fwd_prog_cond_resched();
}
- spin_unlock_irqrestore(&rcu_fwd_lock, flags);
return freed;
}
@@ -1707,6 +1771,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
}
/* Tight loop containing cond_resched(). */
+ WRITE_ONCE(rcu_fwd_cb_nodelay, true);
+ cur_ops->sync(); /* Later readers see above write. */
if (selfpropcb) {
WRITE_ONCE(fcs.stop, 0);
cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
@@ -1724,7 +1790,7 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
udelay(10);
cur_ops->readunlock(idx);
if (!fwd_progress_need_resched || need_resched())
- cond_resched();
+ rcu_torture_fwd_prog_cond_resched();
}
(*tested_tries)++;
if (!time_before(jiffies, stopat) &&
@@ -1745,6 +1811,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
WARN_ON(READ_ONCE(fcs.stop) != 2);
destroy_rcu_head_on_stack(&fcs.rh);
}
+ schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
+ WRITE_ONCE(rcu_fwd_cb_nodelay, false);
}
/* Carry out call_rcu() forward-progress testing. */
@@ -1765,6 +1833,8 @@ static void rcu_torture_fwd_prog_cr(void)
if (READ_ONCE(rcu_fwd_emergency_stop))
return; /* Get out of the way quickly, no GP wait! */
+ if (!cur_ops->call)
+ return; /* Can't do call_rcu() fwd prog without ->call. */
/* Loop continuously posting RCU callbacks. */
WRITE_ONCE(rcu_fwd_cb_nodelay, true);
@@ -1805,7 +1875,7 @@ static void rcu_torture_fwd_prog_cr(void)
rfcp->rfc_gps = 0;
}
cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
- cond_resched();
+ rcu_torture_fwd_prog_cond_resched();
}
stoppedat = jiffies;
n_launders_cb_snap = READ_ONCE(n_launders_cb);
@@ -1814,7 +1884,6 @@ static void rcu_torture_fwd_prog_cr(void)
cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
(void)rcu_torture_fwd_prog_cbfree();
- WRITE_ONCE(rcu_fwd_cb_nodelay, false);
if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop)) {
WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
@@ -1825,6 +1894,8 @@ static void rcu_torture_fwd_prog_cr(void)
n_max_gps, n_max_cbs, cver, gps);
rcu_torture_fwd_cb_hist();
}
+ schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
+ WRITE_ONCE(rcu_fwd_cb_nodelay, false);
}
@@ -2240,7 +2311,7 @@ rcu_torture_init(void)
int firsterr = 0;
static struct rcu_torture_ops *torture_ops[] = {
&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
- &busted_srcud_ops, &tasks_ops,
+ &busted_srcud_ops, &tasks_ops, &trivial_ops,
};
if (!torture_init_begin(torture_type, verbose))
@@ -2363,7 +2434,10 @@ rcu_torture_init(void)
if (stutter < 0)
stutter = 0;
if (stutter) {
- firsterr = torture_stutter_init(stutter * HZ);
+ int t;
+
+ t = cur_ops->stall_dur ? cur_ops->stall_dur() : stutter * HZ;
+ firsterr = torture_stutter_init(stutter * HZ, t);
if (firsterr)
goto unwind;
}
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 9b761e546de8..cf0e886314f2 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -831,8 +831,8 @@ static void srcu_leak_callback(struct rcu_head *rhp)
* srcu_read_lock(), and srcu_read_unlock() that are all passed the same
* srcu_struct structure.
*/
-void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
- rcu_callback_t func, bool do_norm)
+static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
+ rcu_callback_t func, bool do_norm)
{
unsigned long flags;
int idx;
@@ -1310,3 +1310,68 @@ void __init srcu_init(void)
queue_work(rcu_gp_wq, &ssp->work.work);
}
}
+
+#ifdef CONFIG_MODULES
+
+/* Initialize any global-scope srcu_struct structures used by this module. */
+static int srcu_module_coming(struct module *mod)
+{
+ int i;
+ struct srcu_struct **sspp = mod->srcu_struct_ptrs;
+ int ret;
+
+ for (i = 0; i < mod->num_srcu_structs; i++) {
+ ret = init_srcu_struct(*(sspp++));
+ if (WARN_ON_ONCE(ret))
+ return ret;
+ }
+ return 0;
+}
+
+/* Clean up any global-scope srcu_struct structures used by this module. */
+static void srcu_module_going(struct module *mod)
+{
+ int i;
+ struct srcu_struct **sspp = mod->srcu_struct_ptrs;
+
+ for (i = 0; i < mod->num_srcu_structs; i++)
+ cleanup_srcu_struct(*(sspp++));
+}
+
+/* Handle one module, either coming or going. */
+static int srcu_module_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct module *mod = data;
+ int ret = 0;
+
+ switch (val) {
+ case MODULE_STATE_COMING:
+ ret = srcu_module_coming(mod);
+ break;
+ case MODULE_STATE_GOING:
+ srcu_module_going(mod);
+ break;
+ default:
+ break;
+ }
+ return ret;
+}
+
+static struct notifier_block srcu_module_nb = {
+ .notifier_call = srcu_module_notify,
+ .priority = 0,
+};
+
+static __init int init_srcu_module_notifier(void)
+{
+ int ret;
+
+ ret = register_module_notifier(&srcu_module_nb);
+ if (ret)
+ pr_warn("Failed to register srcu module notifier\n");
+ return ret;
+}
+late_initcall(init_srcu_module_notifier);
+
+#endif /* #ifdef CONFIG_MODULES */
diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c
index a8304d90573f..d4558ab7a07d 100644
--- a/kernel/rcu/sync.c
+++ b/kernel/rcu/sync.c
@@ -10,65 +10,18 @@
#include <linux/rcu_sync.h>
#include <linux/sched.h>
-#ifdef CONFIG_PROVE_RCU
-#define __INIT_HELD(func) .held = func,
-#else
-#define __INIT_HELD(func)
-#endif
-
-static const struct {
- void (*sync)(void);
- void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
- void (*wait)(void);
-#ifdef CONFIG_PROVE_RCU
- int (*held)(void);
-#endif
-} gp_ops[] = {
- [RCU_SYNC] = {
- .sync = synchronize_rcu,
- .call = call_rcu,
- .wait = rcu_barrier,
- __INIT_HELD(rcu_read_lock_held)
- },
- [RCU_SCHED_SYNC] = {
- .sync = synchronize_rcu,
- .call = call_rcu,
- .wait = rcu_barrier,
- __INIT_HELD(rcu_read_lock_sched_held)
- },
- [RCU_BH_SYNC] = {
- .sync = synchronize_rcu,
- .call = call_rcu,
- .wait = rcu_barrier,
- __INIT_HELD(rcu_read_lock_bh_held)
- },
-};
-
-enum { GP_IDLE = 0, GP_PENDING, GP_PASSED };
-enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
+enum { GP_IDLE = 0, GP_ENTER, GP_PASSED, GP_EXIT, GP_REPLAY };
#define rss_lock gp_wait.lock
-#ifdef CONFIG_PROVE_RCU
-void rcu_sync_lockdep_assert(struct rcu_sync *rsp)
-{
- RCU_LOCKDEP_WARN(!gp_ops[rsp->gp_type].held(),
- "suspicious rcu_sync_is_idle() usage");
-}
-
-EXPORT_SYMBOL_GPL(rcu_sync_lockdep_assert);
-#endif
-
/**
* rcu_sync_init() - Initialize an rcu_sync structure
* @rsp: Pointer to rcu_sync structure to be initialized
- * @type: Flavor of RCU with which to synchronize rcu_sync structure
*/
-void rcu_sync_init(struct rcu_sync *rsp, enum rcu_sync_type type)
+void rcu_sync_init(struct rcu_sync *rsp)
{
memset(rsp, 0, sizeof(*rsp));
init_waitqueue_head(&rsp->gp_wait);
- rsp->gp_type = type;
}
/**
@@ -86,56 +39,26 @@ void rcu_sync_enter_start(struct rcu_sync *rsp)
rsp->gp_state = GP_PASSED;
}
-/**
- * rcu_sync_enter() - Force readers onto slowpath
- * @rsp: Pointer to rcu_sync structure to use for synchronization
- *
- * This function is used by updaters who need readers to make use of
- * a slowpath during the update. After this function returns, all
- * subsequent calls to rcu_sync_is_idle() will return false, which
- * tells readers to stay off their fastpaths. A later call to
- * rcu_sync_exit() re-enables reader slowpaths.
- *
- * When called in isolation, rcu_sync_enter() must wait for a grace
- * period, however, closely spaced calls to rcu_sync_enter() can
- * optimize away the grace-period wait via a state machine implemented
- * by rcu_sync_enter(), rcu_sync_exit(), and rcu_sync_func().
- */
-void rcu_sync_enter(struct rcu_sync *rsp)
-{
- bool need_wait, need_sync;
- spin_lock_irq(&rsp->rss_lock);
- need_wait = rsp->gp_count++;
- need_sync = rsp->gp_state == GP_IDLE;
- if (need_sync)
- rsp->gp_state = GP_PENDING;
- spin_unlock_irq(&rsp->rss_lock);
+static void rcu_sync_func(struct rcu_head *rhp);
- WARN_ON_ONCE(need_wait && need_sync);
- if (need_sync) {
- gp_ops[rsp->gp_type].sync();
- rsp->gp_state = GP_PASSED;
- wake_up_all(&rsp->gp_wait);
- } else if (need_wait) {
- wait_event(rsp->gp_wait, rsp->gp_state == GP_PASSED);
- } else {
- /*
- * Possible when there's a pending CB from a rcu_sync_exit().
- * Nobody has yet been allowed the 'fast' path and thus we can
- * avoid doing any sync(). The callback will get 'dropped'.
- */
- WARN_ON_ONCE(rsp->gp_state != GP_PASSED);
- }
+static void rcu_sync_call(struct rcu_sync *rsp)
+{
+ call_rcu(&rsp->cb_head, rcu_sync_func);
}
/**
* rcu_sync_func() - Callback function managing reader access to fastpath
* @rhp: Pointer to rcu_head in rcu_sync structure to use for synchronization
*
- * This function is passed to one of the call_rcu() functions by
+ * This function is passed to call_rcu() function by rcu_sync_enter() and
* rcu_sync_exit(), so that it is invoked after a grace period following the
- * that invocation of rcu_sync_exit(). It takes action based on events that
+ * that invocation of enter/exit.
+ *
+ * If it is called by rcu_sync_enter() it signals that all the readers were
+ * switched onto slow path.
+ *
+ * If it is called by rcu_sync_exit() it takes action based on events that
* have taken place in the meantime, so that closely spaced rcu_sync_enter()
* and rcu_sync_exit() pairs need not wait for a grace period.
*
@@ -152,35 +75,88 @@ static void rcu_sync_func(struct rcu_head *rhp)
struct rcu_sync *rsp = container_of(rhp, struct rcu_sync, cb_head);
unsigned long flags;
- WARN_ON_ONCE(rsp->gp_state != GP_PASSED);
- WARN_ON_ONCE(rsp->cb_state == CB_IDLE);
+ WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_IDLE);
+ WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_PASSED);
spin_lock_irqsave(&rsp->rss_lock, flags);
if (rsp->gp_count) {
/*
- * A new rcu_sync_begin() has happened; drop the callback.
+ * We're at least a GP after the GP_IDLE->GP_ENTER transition.
*/
- rsp->cb_state = CB_IDLE;
- } else if (rsp->cb_state == CB_REPLAY) {
+ WRITE_ONCE(rsp->gp_state, GP_PASSED);
+ wake_up_locked(&rsp->gp_wait);
+ } else if (rsp->gp_state == GP_REPLAY) {
/*
- * A new rcu_sync_exit() has happened; requeue the callback
- * to catch a later GP.
+ * A new rcu_sync_exit() has happened; requeue the callback to
+ * catch a later GP.
*/
- rsp->cb_state = CB_PENDING;
- gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func);
+ WRITE_ONCE(rsp->gp_state, GP_EXIT);
+ rcu_sync_call(rsp);
} else {
/*
- * We're at least a GP after rcu_sync_exit(); eveybody will now
- * have observed the write side critical section. Let 'em rip!.
+ * We're at least a GP after the last rcu_sync_exit(); eveybody
+ * will now have observed the write side critical section.
+ * Let 'em rip!.
*/
- rsp->cb_state = CB_IDLE;
- rsp->gp_state = GP_IDLE;
+ WRITE_ONCE(rsp->gp_state, GP_IDLE);
}
spin_unlock_irqrestore(&rsp->rss_lock, flags);
}
/**
- * rcu_sync_exit() - Allow readers back onto fast patch after grace period
+ * rcu_sync_enter() - Force readers onto slowpath
+ * @rsp: Pointer to rcu_sync structure to use for synchronization
+ *
+ * This function is used by updaters who need readers to make use of
+ * a slowpath during the update. After this function returns, all
+ * subsequent calls to rcu_sync_is_idle() will return false, which
+ * tells readers to stay off their fastpaths. A later call to
+ * rcu_sync_exit() re-enables reader slowpaths.
+ *
+ * When called in isolation, rcu_sync_enter() must wait for a grace
+ * period, however, closely spaced calls to rcu_sync_enter() can
+ * optimize away the grace-period wait via a state machine implemented
+ * by rcu_sync_enter(), rcu_sync_exit(), and rcu_sync_func().
+ */
+void rcu_sync_enter(struct rcu_sync *rsp)
+{
+ int gp_state;
+
+ spin_lock_irq(&rsp->rss_lock);
+ gp_state = rsp->gp_state;
+ if (gp_state == GP_IDLE) {
+ WRITE_ONCE(rsp->gp_state, GP_ENTER);
+ WARN_ON_ONCE(rsp->gp_count);
+ /*
+ * Note that we could simply do rcu_sync_call(rsp) here and
+ * avoid the "if (gp_state == GP_IDLE)" block below.
+ *
+ * However, synchronize_rcu() can be faster if rcu_expedited
+ * or rcu_blocking_is_gp() is true.
+ *
+ * Another reason is that we can't wait for rcu callback if
+ * we are called at early boot time but this shouldn't happen.
+ */
+ }
+ rsp->gp_count++;
+ spin_unlock_irq(&rsp->rss_lock);
+
+ if (gp_state == GP_IDLE) {
+ /*
+ * See the comment above, this simply does the "synchronous"
+ * call_rcu(rcu_sync_func) which does GP_ENTER -> GP_PASSED.
+ */
+ synchronize_rcu();
+ rcu_sync_func(&rsp->cb_head);
+ /* Not really needed, wait_event() would see GP_PASSED. */
+ return;
+ }
+
+ wait_event(rsp->gp_wait, READ_ONCE(rsp->gp_state) >= GP_PASSED);
+}
+
+/**
+ * rcu_sync_exit() - Allow readers back onto fast path after grace period
* @rsp: Pointer to rcu_sync structure to use for synchronization
*
* This function is used by updaters who have completed, and can therefore
@@ -191,13 +167,16 @@ static void rcu_sync_func(struct rcu_head *rhp)
*/
void rcu_sync_exit(struct rcu_sync *rsp)
{
+ WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_IDLE);
+ WARN_ON_ONCE(READ_ONCE(rsp->gp_count) == 0);
+
spin_lock_irq(&rsp->rss_lock);
if (!--rsp->gp_count) {
- if (rsp->cb_state == CB_IDLE) {
- rsp->cb_state = CB_PENDING;
- gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func);
- } else if (rsp->cb_state == CB_PENDING) {
- rsp->cb_state = CB_REPLAY;
+ if (rsp->gp_state == GP_PASSED) {
+ WRITE_ONCE(rsp->gp_state, GP_EXIT);
+ rcu_sync_call(rsp);
+ } else if (rsp->gp_state == GP_EXIT) {
+ WRITE_ONCE(rsp->gp_state, GP_REPLAY);
}
}
spin_unlock_irq(&rsp->rss_lock);
@@ -209,18 +188,19 @@ void rcu_sync_exit(struct rcu_sync *rsp)
*/
void rcu_sync_dtor(struct rcu_sync *rsp)
{
- int cb_state;
+ int gp_state;
- WARN_ON_ONCE(rsp->gp_count);
+ WARN_ON_ONCE(READ_ONCE(rsp->gp_count));
+ WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_PASSED);
spin_lock_irq(&rsp->rss_lock);
- if (rsp->cb_state == CB_REPLAY)
- rsp->cb_state = CB_PENDING;
- cb_state = rsp->cb_state;
+ if (rsp->gp_state == GP_REPLAY)
+ WRITE_ONCE(rsp->gp_state, GP_EXIT);
+ gp_state = rsp->gp_state;
spin_unlock_irq(&rsp->rss_lock);
- if (cb_state != CB_IDLE) {
- gp_ops[rsp->gp_type].wait();
- WARN_ON_ONCE(rsp->cb_state != CB_IDLE);
+ if (gp_state != GP_IDLE) {
+ rcu_barrier();
+ WARN_ON_ONCE(rsp->gp_state != GP_IDLE);
}
}
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 980ca3ca643f..a14e5fbbea46 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -51,6 +51,12 @@
#include <linux/tick.h>
#include <linux/sysrq.h>
#include <linux/kprobes.h>
+#include <linux/gfp.h>
+#include <linux/oom.h>
+#include <linux/smpboot.h>
+#include <linux/jiffies.h>
+#include <linux/sched/isolation.h>
+#include "../time/tick-internal.h"
#include "tree.h"
#include "rcu.h"
@@ -92,6 +98,9 @@ struct rcu_state rcu_state = {
/* Dump rcu_node combining tree at boot to verify correct setup. */
static bool dump_tree;
module_param(dump_tree, bool, 0444);
+/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */
+static bool use_softirq = 1;
+module_param(use_softirq, bool, 0444);
/* Control rcu_node-tree auto-balancing at boot time. */
static bool rcu_fanout_exact;
module_param(rcu_fanout_exact, bool, 0444);
@@ -138,7 +147,6 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf);
static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf);
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
static void invoke_rcu_core(void);
-static void invoke_rcu_callbacks(struct rcu_data *rdp);
static void rcu_report_exp_rdp(struct rcu_data *rdp);
static void sync_sched_exp_online_cleanup(int cpu);
@@ -368,19 +376,33 @@ static void __maybe_unused rcu_momentary_dyntick_idle(void)
}
/**
- * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
+ * rcu_is_cpu_rrupt_from_idle - see if interrupted from idle
*
- * If the current CPU is idle or running at a first-level (not nested)
+ * If the current CPU is idle and running at a first-level (not nested)
* interrupt from idle, return true. The caller must have at least
* disabled preemption.
*/
static int rcu_is_cpu_rrupt_from_idle(void)
{
- return __this_cpu_read(rcu_data.dynticks_nesting) <= 0 &&
- __this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 1;
+ /* Called only from within the scheduling-clock interrupt */
+ lockdep_assert_in_irq();
+
+ /* Check for counter underflows */
+ RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0,
+ "RCU dynticks_nesting counter underflow!");
+ RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
+ "RCU dynticks_nmi_nesting counter underflow/zero!");
+
+ /* Are we at first interrupt nesting level? */
+ if (__this_cpu_read(rcu_data.dynticks_nmi_nesting) != 1)
+ return false;
+
+ /* Does CPU appear to be idle from an RCU standpoint? */
+ return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
}
-#define DEFAULT_RCU_BLIMIT 10 /* Maximum callbacks per rcu_do_batch. */
+#define DEFAULT_RCU_BLIMIT 10 /* Maximum callbacks per rcu_do_batch ... */
+#define DEFAULT_MAX_RCU_BLIMIT 10000 /* ... even during callback flood. */
static long blimit = DEFAULT_RCU_BLIMIT;
#define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */
static long qhimark = DEFAULT_RCU_QHIMARK;
@@ -2113,7 +2135,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
/* Reinstate batch limit if we have worked down the excess. */
count = rcu_segcblist_n_cbs(&rdp->cblist);
- if (rdp->blimit == LONG_MAX && count <= qlowmark)
+ if (rdp->blimit >= DEFAULT_MAX_RCU_BLIMIT && count <= qlowmark)
rdp->blimit = blimit;
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
@@ -2253,7 +2275,7 @@ void rcu_force_quiescent_state(void)
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
/* Perform RCU core processing work for the current CPU. */
-static __latent_entropy void rcu_core(struct softirq_action *unused)
+static __latent_entropy void rcu_core(void)
{
unsigned long flags;
struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
@@ -2287,37 +2309,126 @@ static __latent_entropy void rcu_core(struct softirq_action *unused)
rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check());
/* If there are callbacks ready, invoke them. */
- if (rcu_segcblist_ready_cbs(&rdp->cblist))
- invoke_rcu_callbacks(rdp);
+ if (rcu_segcblist_ready_cbs(&rdp->cblist) &&
+ likely(READ_ONCE(rcu_scheduler_fully_active)))
+ rcu_do_batch(rdp);
/* Do any needed deferred wakeups of rcuo kthreads. */
do_nocb_deferred_wakeup(rdp);
trace_rcu_utilization(TPS("End RCU core"));
}
+static void rcu_core_si(struct softirq_action *h)
+{
+ rcu_core();
+}
+
+static void rcu_wake_cond(struct task_struct *t, int status)
+{
+ /*
+ * If the thread is yielding, only wake it when this
+ * is invoked from idle
+ */
+ if (t && (status != RCU_KTHREAD_YIELDING || is_idle_task(current)))
+ wake_up_process(t);
+}
+
+static void invoke_rcu_core_kthread(void)
+{
+ struct task_struct *t;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ __this_cpu_write(rcu_data.rcu_cpu_has_work, 1);
+ t = __this_cpu_read(rcu_data.rcu_cpu_kthread_task);
+ if (t != NULL && t != current)
+ rcu_wake_cond(t, __this_cpu_read(rcu_data.rcu_cpu_kthread_status));
+ local_irq_restore(flags);
+}
+
/*
- * Schedule RCU callback invocation. If the running implementation of RCU
- * does not support RCU priority boosting, just do a direct call, otherwise
- * wake up the per-CPU kernel kthread. Note that because we are running
- * on the current CPU with softirqs disabled, the rcu_cpu_kthread_task
- * cannot disappear out from under us.
+ * Wake up this CPU's rcuc kthread to do RCU core processing.
*/
-static void invoke_rcu_callbacks(struct rcu_data *rdp)
+static void invoke_rcu_core(void)
{
- if (unlikely(!READ_ONCE(rcu_scheduler_fully_active)))
- return;
- if (likely(!rcu_state.boost)) {
- rcu_do_batch(rdp);
+ if (!cpu_online(smp_processor_id()))
return;
+ if (use_softirq)
+ raise_softirq(RCU_SOFTIRQ);
+ else
+ invoke_rcu_core_kthread();
+}
+
+static void rcu_cpu_kthread_park(unsigned int cpu)
+{
+ per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
+}
+
+static int rcu_cpu_kthread_should_run(unsigned int cpu)
+{
+ return __this_cpu_read(rcu_data.rcu_cpu_has_work);
+}
+
+/*
+ * Per-CPU kernel thread that invokes RCU callbacks. This replaces
+ * the RCU softirq used in configurations of RCU that do not support RCU
+ * priority boosting.
+ */
+static void rcu_cpu_kthread(unsigned int cpu)
+{
+ unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status);
+ char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work);
+ int spincnt;
+
+ for (spincnt = 0; spincnt < 10; spincnt++) {
+ trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait"));
+ local_bh_disable();
+ *statusp = RCU_KTHREAD_RUNNING;
+ local_irq_disable();
+ work = *workp;
+ *workp = 0;
+ local_irq_enable();
+ if (work)
+ rcu_core();
+ local_bh_enable();
+ if (*workp == 0) {
+ trace_rcu_utilization(TPS("End CPU kthread@rcu_wait"));
+ *statusp = RCU_KTHREAD_WAITING;
+ return;
+ }
}
- invoke_rcu_callbacks_kthread();
+ *statusp = RCU_KTHREAD_YIELDING;
+ trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield"));
+ schedule_timeout_interruptible(2);
+ trace_rcu_utilization(TPS("End CPU kthread@rcu_yield"));
+ *statusp = RCU_KTHREAD_WAITING;
}
-static void invoke_rcu_core(void)
+static struct smp_hotplug_thread rcu_cpu_thread_spec = {
+ .store = &rcu_data.rcu_cpu_kthread_task,
+ .thread_should_run = rcu_cpu_kthread_should_run,
+ .thread_fn = rcu_cpu_kthread,
+ .thread_comm = "rcuc/%u",
+ .setup = rcu_cpu_kthread_setup,
+ .park = rcu_cpu_kthread_park,
+};
+
+/*
+ * Spawn per-CPU RCU core processing kthreads.
+ */
+static int __init rcu_spawn_core_kthreads(void)
{
- if (cpu_online(smp_processor_id()))
- raise_softirq(RCU_SOFTIRQ);
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0;
+ if (!IS_ENABLED(CONFIG_RCU_BOOST) && use_softirq)
+ return 0;
+ WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec),
+ "%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__);
+ return 0;
}
+early_initcall(rcu_spawn_core_kthreads);
/*
* Handle any core-RCU processing required by a call_rcu() invocation.
@@ -2354,7 +2465,7 @@ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head,
rcu_accelerate_cbs_unlocked(rdp->mynode, rdp);
} else {
/* Give the grace period a kick. */
- rdp->blimit = LONG_MAX;
+ rdp->blimit = DEFAULT_MAX_RCU_BLIMIT;
if (rcu_state.n_force_qs == rdp->n_force_qs_snap &&
rcu_segcblist_first_pend_cb(&rdp->cblist) != head)
rcu_force_quiescent_state();
@@ -3355,7 +3466,8 @@ void __init rcu_init(void)
rcu_init_one();
if (dump_tree)
rcu_dump_rcu_node_tree();
- open_softirq(RCU_SOFTIRQ, rcu_core);
+ if (use_softirq)
+ open_softirq(RCU_SOFTIRQ, rcu_core_si);
/*
* We don't need protection against CPU-hotplug here because
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index e253d11af3c4..7acaf3a62d39 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -154,13 +154,15 @@ struct rcu_data {
bool core_needs_qs; /* Core waits for quiesc state. */
bool beenonline; /* CPU online at least once. */
bool gpwrap; /* Possible ->gp_seq wrap. */
- bool deferred_qs; /* This CPU awaiting a deferred QS? */
+ bool exp_deferred_qs; /* This CPU awaiting a deferred QS? */
struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
unsigned long grpmask; /* Mask to apply to leaf qsmask. */
unsigned long ticks_this_gp; /* The number of scheduling-clock */
/* ticks this CPU has handled */
/* during and after the last grace */
/* period it is aware of. */
+ struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
+ bool defer_qs_iw_pending; /* Scheduler attention pending? */
/* 2) batch handling */
struct rcu_segcblist cblist; /* Segmented callback list, with */
@@ -407,8 +409,8 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func);
static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
-static void invoke_rcu_callbacks_kthread(void);
static bool rcu_is_callbacks_kthread(void);
+static void rcu_cpu_kthread_setup(unsigned int cpu);
static void __init rcu_spawn_boost_kthreads(void);
static void rcu_prepare_kthreads(int cpu);
static void rcu_cleanup_after_idle(void);
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 9c990df880d1..af7e7b9c86af 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -250,7 +250,7 @@ static void rcu_report_exp_cpu_mult(struct rcu_node *rnp,
*/
static void rcu_report_exp_rdp(struct rcu_data *rdp)
{
- WRITE_ONCE(rdp->deferred_qs, false);
+ WRITE_ONCE(rdp->exp_deferred_qs, false);
rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true);
}
@@ -259,8 +259,7 @@ static bool sync_exp_work_done(unsigned long s)
{
if (rcu_exp_gp_seq_done(s)) {
trace_rcu_exp_grace_period(rcu_state.name, s, TPS("done"));
- /* Ensure test happens before caller kfree(). */
- smp_mb__before_atomic(); /* ^^^ */
+ smp_mb(); /* Ensure test happens before caller kfree(). */
return true;
}
return false;
@@ -384,7 +383,12 @@ retry_ipi:
mask_ofl_test |= mask;
continue;
}
+ if (get_cpu() == cpu) {
+ put_cpu();
+ continue;
+ }
ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0);
+ put_cpu();
if (!ret) {
mask_ofl_ipi &= ~mask;
continue;
@@ -611,7 +615,7 @@ static void rcu_exp_handler(void *unused)
rcu_dynticks_curr_cpu_in_eqs()) {
rcu_report_exp_rdp(rdp);
} else {
- rdp->deferred_qs = true;
+ rdp->exp_deferred_qs = true;
set_tsk_need_resched(t);
set_preempt_need_resched();
}
@@ -633,7 +637,7 @@ static void rcu_exp_handler(void *unused)
if (t->rcu_read_lock_nesting > 0) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (rnp->expmask & rdp->grpmask) {
- rdp->deferred_qs = true;
+ rdp->exp_deferred_qs = true;
t->rcu_read_unlock_special.b.exp_hint = true;
}
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
@@ -656,7 +660,7 @@ static void rcu_exp_handler(void *unused)
*
* Otherwise, force a context switch after the CPU enables everything.
*/
- rdp->deferred_qs = true;
+ rdp->exp_deferred_qs = true;
if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs())) {
rcu_preempt_deferred_qs(t);
@@ -694,6 +698,16 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
#else /* #ifdef CONFIG_PREEMPT_RCU */
+/* Request an expedited quiescent state. */
+static void rcu_exp_need_qs(void)
+{
+ __this_cpu_write(rcu_data.cpu_no_qs.b.exp, true);
+ /* Store .exp before .rcu_urgent_qs. */
+ smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true);
+ set_tsk_need_resched(current);
+ set_preempt_need_resched();
+}
+
/* Invoked on each online non-idle CPU for expedited quiescent state. */
static void rcu_exp_handler(void *unused)
{
@@ -709,25 +723,38 @@ static void rcu_exp_handler(void *unused)
rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
return;
}
- __this_cpu_write(rcu_data.cpu_no_qs.b.exp, true);
- /* Store .exp before .rcu_urgent_qs. */
- smp_store_release(this_cpu_ptr(&rcu_data.rcu_urgent_qs), true);
- set_tsk_need_resched(current);
- set_preempt_need_resched();
+ rcu_exp_need_qs();
}
/* Send IPI for expedited cleanup if needed at end of CPU-hotplug operation. */
static void sync_sched_exp_online_cleanup(int cpu)
{
+ unsigned long flags;
+ int my_cpu;
struct rcu_data *rdp;
int ret;
struct rcu_node *rnp;
rdp = per_cpu_ptr(&rcu_data, cpu);
rnp = rdp->mynode;
- if (!(READ_ONCE(rnp->expmask) & rdp->grpmask))
+ my_cpu = get_cpu();
+ /* Quiescent state either not needed or already requested, leave. */
+ if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
+ __this_cpu_read(rcu_data.cpu_no_qs.b.exp)) {
+ put_cpu();
+ return;
+ }
+ /* Quiescent state needed on current CPU, so set it up locally. */
+ if (my_cpu == cpu) {
+ local_irq_save(flags);
+ rcu_exp_need_qs();
+ local_irq_restore(flags);
+ put_cpu();
return;
+ }
+ /* Quiescent state needed on some other CPU, send IPI. */
ret = smp_call_function_single(cpu, rcu_exp_handler, NULL, 0);
+ put_cpu();
WARN_ON_ONCE(ret);
}
@@ -765,7 +792,6 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
*/
void synchronize_rcu_expedited(void)
{
- struct rcu_data *rdp;
struct rcu_exp_work rew;
struct rcu_node *rnp;
unsigned long s;
@@ -802,7 +828,6 @@ void synchronize_rcu_expedited(void)
}
/* Wait for expedited grace period to complete. */
- rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id());
rnp = rcu_get_root();
wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
sync_exp_work_done(s));
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 1102765f91fd..acb225023ed1 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -11,29 +11,7 @@
* Paul E. McKenney <paulmck@linux.ibm.com>
*/
-#include <linux/delay.h>
-#include <linux/gfp.h>
-#include <linux/oom.h>
-#include <linux/sched/debug.h>
-#include <linux/smpboot.h>
-#include <linux/sched/isolation.h>
-#include <uapi/linux/sched/types.h>
-#include "../time/tick-internal.h"
-
-#ifdef CONFIG_RCU_BOOST
#include "../locking/rtmutex_common.h"
-#else /* #ifdef CONFIG_RCU_BOOST */
-
-/*
- * Some architectures do not define rt_mutexes, but if !CONFIG_RCU_BOOST,
- * all uses are in dead code. Provide a definition to keep the compiler
- * happy, but add WARN_ON_ONCE() to complain if used in the wrong place.
- * This probably needs to be excluded from -rt builds.
- */
-#define rt_mutex_owner(a) ({ WARN_ON_ONCE(1); NULL; })
-#define rt_mutex_futex_unlock(x) WARN_ON_ONCE(1)
-
-#endif /* #else #ifdef CONFIG_RCU_BOOST */
#ifdef CONFIG_RCU_NOCB_CPU
static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
@@ -94,6 +72,8 @@ static void __init rcu_bootup_announce_oddness(void)
pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay);
if (gp_cleanup_delay)
pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay);
+ if (!use_softirq)
+ pr_info("\tRCU_SOFTIRQ processing moved to rcuc kthreads.\n");
if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG))
pr_info("\tRCU debug extended QS entry/exit.\n");
rcupdate_announce_bootup_oddness();
@@ -257,10 +237,10 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
* no need to check for a subsequent expedited GP. (Though we are
* still in a quiescent state in any case.)
*/
- if (blkd_state & RCU_EXP_BLKD && rdp->deferred_qs)
+ if (blkd_state & RCU_EXP_BLKD && rdp->exp_deferred_qs)
rcu_report_exp_rdp(rdp);
else
- WARN_ON_ONCE(rdp->deferred_qs);
+ WARN_ON_ONCE(rdp->exp_deferred_qs);
}
/*
@@ -357,7 +337,7 @@ void rcu_note_context_switch(bool preempt)
* means that we continue to block the current grace period.
*/
rcu_qs();
- if (rdp->deferred_qs)
+ if (rdp->exp_deferred_qs)
rcu_report_exp_rdp(rdp);
trace_rcu_utilization(TPS("End context switch"));
barrier(); /* Avoid RCU read-side critical sections leaking up. */
@@ -471,14 +451,15 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
*/
special = t->rcu_read_unlock_special;
rdp = this_cpu_ptr(&rcu_data);
- if (!special.s && !rdp->deferred_qs) {
+ if (!special.s && !rdp->exp_deferred_qs) {
local_irq_restore(flags);
return;
}
+ t->rcu_read_unlock_special.b.deferred_qs = false;
if (special.b.need_qs) {
rcu_qs();
t->rcu_read_unlock_special.b.need_qs = false;
- if (!t->rcu_read_unlock_special.s && !rdp->deferred_qs) {
+ if (!t->rcu_read_unlock_special.s && !rdp->exp_deferred_qs) {
local_irq_restore(flags);
return;
}
@@ -490,7 +471,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
* tasks are handled when removing the task from the
* blocked-tasks list below.
*/
- if (rdp->deferred_qs) {
+ if (rdp->exp_deferred_qs) {
rcu_report_exp_rdp(rdp);
if (!t->rcu_read_unlock_special.s) {
local_irq_restore(flags);
@@ -579,7 +560,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
*/
static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
{
- return (__this_cpu_read(rcu_data.deferred_qs) ||
+ return (__this_cpu_read(rcu_data.exp_deferred_qs) ||
READ_ONCE(t->rcu_read_unlock_special.s)) &&
t->rcu_read_lock_nesting <= 0;
}
@@ -607,6 +588,17 @@ static void rcu_preempt_deferred_qs(struct task_struct *t)
}
/*
+ * Minimal handler to give the scheduler a chance to re-evaluate.
+ */
+static void rcu_preempt_deferred_qs_handler(struct irq_work *iwp)
+{
+ struct rcu_data *rdp;
+
+ rdp = container_of(iwp, struct rcu_data, defer_qs_iw);
+ rdp->defer_qs_iw_pending = false;
+}
+
+/*
* 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.
@@ -625,16 +617,41 @@ static void rcu_read_unlock_special(struct task_struct *t)
local_irq_save(flags);
irqs_were_disabled = irqs_disabled_flags(flags);
if (preempt_bh_were_disabled || irqs_were_disabled) {
- WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, false);
- /* Need to defer quiescent state until everything is enabled. */
- if (irqs_were_disabled) {
- /* Enabling irqs does not reschedule, so... */
+ bool exp;
+ struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ struct rcu_node *rnp = rdp->mynode;
+
+ t->rcu_read_unlock_special.b.exp_hint = false;
+ exp = (t->rcu_blocked_node && t->rcu_blocked_node->exp_tasks) ||
+ (rdp->grpmask & rnp->expmask) ||
+ tick_nohz_full_cpu(rdp->cpu);
+ // Need to defer quiescent state until everything is enabled.
+ if ((exp || in_irq()) && irqs_were_disabled && use_softirq &&
+ (in_irq() || !t->rcu_read_unlock_special.b.deferred_qs)) {
+ // Using softirq, safe to awaken, and we get
+ // no help from enabling irqs, unlike bh/preempt.
raise_softirq_irqoff(RCU_SOFTIRQ);
+ } else if (exp && irqs_were_disabled && !use_softirq &&
+ !t->rcu_read_unlock_special.b.deferred_qs) {
+ // Safe to awaken and we get no help from enabling
+ // irqs, unlike bh/preempt.
+ invoke_rcu_core();
} else {
- /* Enabling BH or preempt does reschedule, so... */
+ // Enabling BH or preempt does reschedule, so...
+ // Also if no expediting or NO_HZ_FULL, slow is OK.
set_tsk_need_resched(current);
set_preempt_need_resched();
+ if (IS_ENABLED(CONFIG_IRQ_WORK) &&
+ !rdp->defer_qs_iw_pending && exp) {
+ // Get scheduler to re-evaluate and call hooks.
+ // If !IRQ_WORK, FQS scan will eventually IPI.
+ init_irq_work(&rdp->defer_qs_iw,
+ rcu_preempt_deferred_qs_handler);
+ rdp->defer_qs_iw_pending = true;
+ irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);
+ }
}
+ t->rcu_read_unlock_special.b.deferred_qs = true;
local_irq_restore(flags);
return;
}
@@ -760,7 +777,7 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
i = 0;
list_for_each(lhp, &rnp->blkd_tasks) {
pr_cont(" %p", lhp);
- if (++i >= 10)
+ if (++i >= ncheck)
break;
}
pr_cont("\n");
@@ -944,18 +961,21 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
+/*
+ * If boosting, set rcuc kthreads to realtime priority.
+ */
+static void rcu_cpu_kthread_setup(unsigned int cpu)
+{
#ifdef CONFIG_RCU_BOOST
+ struct sched_param sp;
-static void rcu_wake_cond(struct task_struct *t, int status)
-{
- /*
- * If the thread is yielding, only wake it when this
- * is invoked from idle
- */
- if (status != RCU_KTHREAD_YIELDING || is_idle_task(current))
- wake_up_process(t);
+ sp.sched_priority = kthread_prio;
+ sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
+#endif /* #ifdef CONFIG_RCU_BOOST */
}
+#ifdef CONFIG_RCU_BOOST
+
/*
* Carry out RCU priority boosting on the task indicated by ->exp_tasks
* or ->boost_tasks, advancing the pointer to the next task in the
@@ -1091,23 +1111,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
}
/*
- * Wake up the per-CPU kthread to invoke RCU callbacks.
- */
-static void invoke_rcu_callbacks_kthread(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- __this_cpu_write(rcu_data.rcu_cpu_has_work, 1);
- if (__this_cpu_read(rcu_data.rcu_cpu_kthread_task) != NULL &&
- current != __this_cpu_read(rcu_data.rcu_cpu_kthread_task)) {
- rcu_wake_cond(__this_cpu_read(rcu_data.rcu_cpu_kthread_task),
- __this_cpu_read(rcu_data.rcu_cpu_kthread_status));
- }
- local_irq_restore(flags);
-}
-
-/*
* Is the current CPU running the RCU-callbacks kthread?
* Caller must have preemption disabled.
*/
@@ -1160,59 +1163,6 @@ static int rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
return 0;
}
-static void rcu_cpu_kthread_setup(unsigned int cpu)
-{
- struct sched_param sp;
-
- sp.sched_priority = kthread_prio;
- sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
-}
-
-static void rcu_cpu_kthread_park(unsigned int cpu)
-{
- per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
-}
-
-static int rcu_cpu_kthread_should_run(unsigned int cpu)
-{
- return __this_cpu_read(rcu_data.rcu_cpu_has_work);
-}
-
-/*
- * Per-CPU kernel thread that invokes RCU callbacks. This replaces
- * the RCU softirq used in configurations of RCU that do not support RCU
- * priority boosting.
- */
-static void rcu_cpu_kthread(unsigned int cpu)
-{
- unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status);
- char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work);
- int spincnt;
-
- for (spincnt = 0; spincnt < 10; spincnt++) {
- trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait"));
- local_bh_disable();
- *statusp = RCU_KTHREAD_RUNNING;
- local_irq_disable();
- work = *workp;
- *workp = 0;
- local_irq_enable();
- if (work)
- rcu_do_batch(this_cpu_ptr(&rcu_data));
- local_bh_enable();
- if (*workp == 0) {
- trace_rcu_utilization(TPS("End CPU kthread@rcu_wait"));
- *statusp = RCU_KTHREAD_WAITING;
- return;
- }
- }
- *statusp = RCU_KTHREAD_YIELDING;
- trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield"));
- schedule_timeout_interruptible(2);
- trace_rcu_utilization(TPS("End CPU kthread@rcu_yield"));
- *statusp = RCU_KTHREAD_WAITING;
-}
-
/*
* Set the per-rcu_node kthread's affinity to cover all CPUs that are
* served by the rcu_node in question. The CPU hotplug lock is still
@@ -1243,27 +1193,13 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
free_cpumask_var(cm);
}
-static struct smp_hotplug_thread rcu_cpu_thread_spec = {
- .store = &rcu_data.rcu_cpu_kthread_task,
- .thread_should_run = rcu_cpu_kthread_should_run,
- .thread_fn = rcu_cpu_kthread,
- .thread_comm = "rcuc/%u",
- .setup = rcu_cpu_kthread_setup,
- .park = rcu_cpu_kthread_park,
-};
-
/*
* Spawn boost kthreads -- called as soon as the scheduler is running.
*/
static void __init rcu_spawn_boost_kthreads(void)
{
struct rcu_node *rnp;
- int cpu;
- for_each_possible_cpu(cpu)
- per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0;
- if (WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), "%s: Could not start rcub kthread, OOM is now expected behavior\n", __func__))
- return;
rcu_for_each_leaf_node(rnp)
(void)rcu_spawn_one_boost_kthread(rnp);
}
@@ -1286,11 +1222,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
-static void invoke_rcu_callbacks_kthread(void)
-{
- WARN_ON_ONCE(1);
-}
-
static bool rcu_is_callbacks_kthread(void)
{
return false;
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index f65a73a97323..065183391f75 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -630,7 +630,9 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
time_before(j, rcu_state.gp_activity + gpssdelay) ||
atomic_xchg(&warned, 1)) {
- raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */
+ if (rnp_root != rnp)
+ /* irqs remain disabled. */
+ raw_spin_unlock_rcu_node(rnp_root);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return;
}
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index c3bf44ba42e5..61df2bf08563 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -423,6 +423,19 @@ EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
do { } while (0)
#endif
+#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
+/* Get rcutorture access to sched_setaffinity(). */
+long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
+{
+ int ret;
+
+ ret = sched_setaffinity(pid, in_mask);
+ WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
+#endif
+
#ifdef CONFIG_RCU_STALL_COMMON
int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
diff --git a/kernel/torture.c b/kernel/torture.c
index 17b2be9bde12..a8d9bdfba7c3 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -570,6 +570,7 @@ static void torture_shutdown_cleanup(void)
static struct task_struct *stutter_task;
static int stutter_pause_test;
static int stutter;
+static int stutter_gap;
/*
* Block until the stutter interval ends. This must be called periodically
@@ -578,10 +579,12 @@ static int stutter;
bool stutter_wait(const char *title)
{
int spt;
+ bool ret = false;
cond_resched_tasks_rcu_qs();
spt = READ_ONCE(stutter_pause_test);
for (; spt; spt = READ_ONCE(stutter_pause_test)) {
+ ret = true;
if (spt == 1) {
schedule_timeout_interruptible(1);
} else if (spt == 2) {
@@ -592,7 +595,7 @@ bool stutter_wait(const char *title)
}
torture_shutdown_absorb(title);
}
- return !!spt;
+ return ret;
}
EXPORT_SYMBOL_GPL(stutter_wait);
@@ -602,17 +605,24 @@ EXPORT_SYMBOL_GPL(stutter_wait);
*/
static int torture_stutter(void *arg)
{
+ int wtime;
+
VERBOSE_TOROUT_STRING("torture_stutter task started");
do {
if (!torture_must_stop() && stutter > 1) {
- WRITE_ONCE(stutter_pause_test, 1);
- schedule_timeout_interruptible(stutter - 1);
+ wtime = stutter;
+ if (stutter > HZ + 1) {
+ WRITE_ONCE(stutter_pause_test, 1);
+ wtime = stutter - HZ - 1;
+ schedule_timeout_interruptible(wtime);
+ wtime = HZ + 1;
+ }
WRITE_ONCE(stutter_pause_test, 2);
- schedule_timeout_interruptible(1);
+ schedule_timeout_interruptible(wtime);
}
WRITE_ONCE(stutter_pause_test, 0);
if (!torture_must_stop())
- schedule_timeout_interruptible(stutter);
+ schedule_timeout_interruptible(stutter_gap);
torture_shutdown_absorb("torture_stutter");
} while (!torture_must_stop());
torture_kthread_stopping("torture_stutter");
@@ -622,9 +632,10 @@ static int torture_stutter(void *arg)
/*
* Initialize and kick off the torture_stutter kthread.
*/
-int torture_stutter_init(const int s)
+int torture_stutter_init(const int s, const int sgap)
{
stutter = s;
+ stutter_gap = sgap;
return torture_create_kthread(torture_stutter, NULL, stutter_task);
}
EXPORT_SYMBOL_GPL(torture_stutter_init);