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-rw-r--r--kernel/rcu/Makefile3
-rw-r--r--kernel/rcu/rcu.h6
-rw-r--r--kernel/rcu/rcutorture.c66
-rw-r--r--kernel/rcu/srcu.c2
-rw-r--r--kernel/rcu/tiny.c111
-rw-r--r--kernel/rcu/tiny_plugin.h2
-rw-r--r--kernel/rcu/tree.c158
-rw-r--r--kernel/rcu/tree.h55
-rw-r--r--kernel/rcu/tree_plugin.h261
9 files changed, 226 insertions, 438 deletions
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index e6fae50..50a8084 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -1,4 +1,5 @@
-obj-y += update.o srcu.o
+obj-y += update.o
+obj-$(CONFIG_SRCU) += srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
obj-$(CONFIG_TREE_RCU) += tree.o
obj-$(CONFIG_PREEMPT_RCU) += tree.o
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 07bb02e..80adef7 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -137,4 +137,10 @@ int rcu_jiffies_till_stall_check(void);
void rcu_early_boot_tests(void);
+/*
+ * This function really isn't for public consumption, but RCU is special in
+ * that context switches can allow the state machine to make progress.
+ */
+extern void resched_cpu(int cpu);
+
#endif /* __LINUX_RCU_H */
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 4d559ba..30d42aa 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -244,7 +244,8 @@ struct rcu_torture_ops {
int (*readlock)(void);
void (*read_delay)(struct torture_random_state *rrsp);
void (*readunlock)(int idx);
- int (*completed)(void);
+ unsigned long (*started)(void);
+ unsigned long (*completed)(void);
void (*deferred_free)(struct rcu_torture *p);
void (*sync)(void);
void (*exp_sync)(void);
@@ -296,11 +297,6 @@ static void rcu_torture_read_unlock(int idx) __releases(RCU)
rcu_read_unlock();
}
-static int rcu_torture_completed(void)
-{
- return rcu_batches_completed();
-}
-
/*
* Update callback in the pipe. This should be invoked after a grace period.
*/
@@ -356,7 +352,7 @@ rcu_torture_cb(struct rcu_head *p)
cur_ops->deferred_free(rp);
}
-static int rcu_no_completed(void)
+static unsigned long rcu_no_completed(void)
{
return 0;
}
@@ -377,7 +373,8 @@ static struct rcu_torture_ops rcu_ops = {
.readlock = rcu_torture_read_lock,
.read_delay = rcu_read_delay,
.readunlock = rcu_torture_read_unlock,
- .completed = rcu_torture_completed,
+ .started = rcu_batches_started,
+ .completed = rcu_batches_completed,
.deferred_free = rcu_torture_deferred_free,
.sync = synchronize_rcu,
.exp_sync = synchronize_rcu_expedited,
@@ -407,11 +404,6 @@ static void rcu_bh_torture_read_unlock(int idx) __releases(RCU_BH)
rcu_read_unlock_bh();
}
-static int rcu_bh_torture_completed(void)
-{
- return rcu_batches_completed_bh();
-}
-
static void rcu_bh_torture_deferred_free(struct rcu_torture *p)
{
call_rcu_bh(&p->rtort_rcu, rcu_torture_cb);
@@ -423,7 +415,8 @@ static struct rcu_torture_ops rcu_bh_ops = {
.readlock = rcu_bh_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_bh_torture_read_unlock,
- .completed = rcu_bh_torture_completed,
+ .started = rcu_batches_started_bh,
+ .completed = rcu_batches_completed_bh,
.deferred_free = rcu_bh_torture_deferred_free,
.sync = synchronize_rcu_bh,
.exp_sync = synchronize_rcu_bh_expedited,
@@ -466,6 +459,7 @@ static struct rcu_torture_ops rcu_busted_ops = {
.readlock = rcu_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_torture_read_unlock,
+ .started = rcu_no_completed,
.completed = rcu_no_completed,
.deferred_free = rcu_busted_torture_deferred_free,
.sync = synchronize_rcu_busted,
@@ -510,7 +504,7 @@ static void srcu_torture_read_unlock(int idx) __releases(&srcu_ctl)
srcu_read_unlock(&srcu_ctl, idx);
}
-static int srcu_torture_completed(void)
+static unsigned long srcu_torture_completed(void)
{
return srcu_batches_completed(&srcu_ctl);
}
@@ -564,6 +558,7 @@ static struct rcu_torture_ops srcu_ops = {
.readlock = srcu_torture_read_lock,
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock,
+ .started = NULL,
.completed = srcu_torture_completed,
.deferred_free = srcu_torture_deferred_free,
.sync = srcu_torture_synchronize,
@@ -600,7 +595,8 @@ 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 = rcu_no_completed,
+ .started = rcu_batches_started_sched,
+ .completed = rcu_batches_completed_sched,
.deferred_free = rcu_sched_torture_deferred_free,
.sync = synchronize_sched,
.exp_sync = synchronize_sched_expedited,
@@ -638,6 +634,7 @@ static struct rcu_torture_ops tasks_ops = {
.readlock = tasks_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = tasks_torture_read_unlock,
+ .started = rcu_no_completed,
.completed = rcu_no_completed,
.deferred_free = rcu_tasks_torture_deferred_free,
.sync = synchronize_rcu_tasks,
@@ -1015,8 +1012,8 @@ static void rcutorture_trace_dump(void)
static void rcu_torture_timer(unsigned long unused)
{
int idx;
- int completed;
- int completed_end;
+ unsigned long started;
+ unsigned long completed;
static DEFINE_TORTURE_RANDOM(rand);
static DEFINE_SPINLOCK(rand_lock);
struct rcu_torture *p;
@@ -1024,7 +1021,10 @@ static void rcu_torture_timer(unsigned long unused)
unsigned long long ts;
idx = cur_ops->readlock();
- completed = cur_ops->completed();
+ if (cur_ops->started)
+ started = cur_ops->started();
+ else
+ started = cur_ops->completed();
ts = rcu_trace_clock_local();
p = rcu_dereference_check(rcu_torture_current,
rcu_read_lock_bh_held() ||
@@ -1047,14 +1047,16 @@ static void rcu_torture_timer(unsigned long unused)
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
}
- completed_end = cur_ops->completed();
+ completed = cur_ops->completed();
if (pipe_count > 1) {
do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,
- completed, completed_end);
+ started, completed);
rcutorture_trace_dump();
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
- completed = completed_end - completed;
+ completed = completed - started;
+ if (cur_ops->started)
+ completed++;
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
@@ -1073,8 +1075,8 @@ static void rcu_torture_timer(unsigned long unused)
static int
rcu_torture_reader(void *arg)
{
- int completed;
- int completed_end;
+ unsigned long started;
+ unsigned long completed;
int idx;
DEFINE_TORTURE_RANDOM(rand);
struct rcu_torture *p;
@@ -1093,7 +1095,10 @@ rcu_torture_reader(void *arg)
mod_timer(&t, jiffies + 1);
}
idx = cur_ops->readlock();
- completed = cur_ops->completed();
+ if (cur_ops->started)
+ started = cur_ops->started();
+ else
+ started = cur_ops->completed();
ts = rcu_trace_clock_local();
p = rcu_dereference_check(rcu_torture_current,
rcu_read_lock_bh_held() ||
@@ -1114,14 +1119,16 @@ rcu_torture_reader(void *arg)
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
}
- completed_end = cur_ops->completed();
+ completed = cur_ops->completed();
if (pipe_count > 1) {
do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
- ts, completed, completed_end);
+ ts, started, completed);
rcutorture_trace_dump();
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
- completed = completed_end - completed;
+ completed = completed - started;
+ if (cur_ops->started)
+ completed++;
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
@@ -1420,6 +1427,9 @@ static int rcu_torture_barrier(void *arg)
cur_ops->cb_barrier(); /* Implies smp_mb() for wait_event(). */
if (atomic_read(&barrier_cbs_invoked) != n_barrier_cbs) {
n_rcu_torture_barrier_error++;
+ pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
+ atomic_read(&barrier_cbs_invoked),
+ n_barrier_cbs);
WARN_ON_ONCE(1);
}
n_barrier_successes++;
diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index e037f3e..445bf8f 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -546,7 +546,7 @@ EXPORT_SYMBOL_GPL(srcu_barrier);
* Report the number of batches, correlated with, but not necessarily
* precisely the same as, the number of grace periods that have elapsed.
*/
-long srcu_batches_completed(struct srcu_struct *sp)
+unsigned long srcu_batches_completed(struct srcu_struct *sp)
{
return sp->completed;
}
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index fc0f2c0..cc9ceca 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -47,54 +47,14 @@ static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp);
-static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
-
#include "tiny_plugin.h"
-/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcu/tree.c. */
-static void rcu_idle_enter_common(long long newval)
-{
- if (newval) {
- RCU_TRACE(trace_rcu_dyntick(TPS("--="),
- rcu_dynticks_nesting, newval));
- rcu_dynticks_nesting = newval;
- return;
- }
- RCU_TRACE(trace_rcu_dyntick(TPS("Start"),
- rcu_dynticks_nesting, newval));
- if (IS_ENABLED(CONFIG_RCU_TRACE) && !is_idle_task(current)) {
- struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());
-
- RCU_TRACE(trace_rcu_dyntick(TPS("Entry error: not idle task"),
- rcu_dynticks_nesting, newval));
- ftrace_dump(DUMP_ALL);
- WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
- current->pid, current->comm,
- idle->pid, idle->comm); /* must be idle task! */
- }
- rcu_sched_qs(); /* implies rcu_bh_inc() */
- barrier();
- rcu_dynticks_nesting = newval;
-}
-
/*
* Enter idle, which is an extended quiescent state if we have fully
- * entered that mode (i.e., if the new value of dynticks_nesting is zero).
+ * entered that mode.
*/
void rcu_idle_enter(void)
{
- unsigned long flags;
- long long newval;
-
- local_irq_save(flags);
- WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0);
- if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) ==
- DYNTICK_TASK_NEST_VALUE)
- newval = 0;
- else
- newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE;
- rcu_idle_enter_common(newval);
- local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_idle_enter);
@@ -103,55 +63,14 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter);
*/
void rcu_irq_exit(void)
{
- unsigned long flags;
- long long newval;
-
- local_irq_save(flags);
- newval = rcu_dynticks_nesting - 1;
- WARN_ON_ONCE(newval < 0);
- rcu_idle_enter_common(newval);
- local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_irq_exit);
-/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcu/tree.c. */
-static void rcu_idle_exit_common(long long oldval)
-{
- if (oldval) {
- RCU_TRACE(trace_rcu_dyntick(TPS("++="),
- oldval, rcu_dynticks_nesting));
- return;
- }
- RCU_TRACE(trace_rcu_dyntick(TPS("End"), oldval, rcu_dynticks_nesting));
- if (IS_ENABLED(CONFIG_RCU_TRACE) && !is_idle_task(current)) {
- struct task_struct *idle __maybe_unused = idle_task(smp_processor_id());
-
- RCU_TRACE(trace_rcu_dyntick(TPS("Exit error: not idle task"),
- oldval, rcu_dynticks_nesting));
- ftrace_dump(DUMP_ALL);
- WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
- current->pid, current->comm,
- idle->pid, idle->comm); /* must be idle task! */
- }
-}
-
/*
* Exit idle, so that we are no longer in an extended quiescent state.
*/
void rcu_idle_exit(void)
{
- unsigned long flags;
- long long oldval;
-
- local_irq_save(flags);
- oldval = rcu_dynticks_nesting;
- WARN_ON_ONCE(rcu_dynticks_nesting < 0);
- if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK)
- rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
- else
- rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
- rcu_idle_exit_common(oldval);
- local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_idle_exit);
@@ -160,15 +79,6 @@ EXPORT_SYMBOL_GPL(rcu_idle_exit);
*/
void rcu_irq_enter(void)
{
- unsigned long flags;
- long long oldval;
-
- local_irq_save(flags);
- oldval = rcu_dynticks_nesting;
- rcu_dynticks_nesting++;
- WARN_ON_ONCE(rcu_dynticks_nesting == 0);
- rcu_idle_exit_common(oldval);
- local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(rcu_irq_enter);
@@ -179,23 +89,13 @@ EXPORT_SYMBOL_GPL(rcu_irq_enter);
*/
bool notrace __rcu_is_watching(void)
{
- return rcu_dynticks_nesting;
+ return true;
}
EXPORT_SYMBOL(__rcu_is_watching);
#endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
/*
- * Test whether the current CPU was interrupted from idle. Nested
- * interrupts don't count, we must be running at the first interrupt
- * level.
- */
-static int rcu_is_cpu_rrupt_from_idle(void)
-{
- return rcu_dynticks_nesting <= 1;
-}
-
-/*
* Helper function for rcu_sched_qs() and rcu_bh_qs().
* Also irqs are disabled to avoid confusion due to interrupt handlers
* invoking call_rcu().
@@ -250,7 +150,7 @@ void rcu_bh_qs(void)
void rcu_check_callbacks(int user)
{
RCU_TRACE(check_cpu_stalls());
- if (user || rcu_is_cpu_rrupt_from_idle())
+ if (user)
rcu_sched_qs();
else if (!in_softirq())
rcu_bh_qs();
@@ -357,6 +257,11 @@ static void __call_rcu(struct rcu_head *head,
rcp->curtail = &head->next;
RCU_TRACE(rcp->qlen++);
local_irq_restore(flags);
+
+ if (unlikely(is_idle_task(current))) {
+ /* force scheduling for rcu_sched_qs() */
+ resched_cpu(0);
+ }
}
/*
diff --git a/kernel/rcu/tiny_plugin.h b/kernel/rcu/tiny_plugin.h
index 80f908a..f94e209 100644
--- a/kernel/rcu/tiny_plugin.h
+++ b/kernel/rcu/tiny_plugin.h
@@ -147,7 +147,7 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
js = ACCESS_ONCE(rcp->jiffies_stall);
if (rcp->rcucblist && ULONG_CMP_GE(j, js)) {
pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
- rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
+ rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE,
jiffies - rcp->gp_start, rcp->qlen);
dump_stack();
ACCESS_ONCE(rcp->jiffies_stall) = jiffies +
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e335f33..48d640c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -338,18 +338,54 @@ static void force_quiescent_state(struct rcu_state *rsp);
static int rcu_pending(void);
/*
- * Return the number of RCU-sched batches processed thus far for debug & stats.
+ * Return the number of RCU batches started thus far for debug & stats.
*/
-long rcu_batches_completed_sched(void)
+unsigned long rcu_batches_started(void)
+{
+ return rcu_state_p->gpnum;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_started);
+
+/*
+ * Return the number of RCU-sched batches started thus far for debug & stats.
+ */
+unsigned long rcu_batches_started_sched(void)
+{
+ return rcu_sched_state.gpnum;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_started_sched);
+
+/*
+ * Return the number of RCU BH batches started thus far for debug & stats.
+ */
+unsigned long rcu_batches_started_bh(void)
+{
+ return rcu_bh_state.gpnum;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_started_bh);
+
+/*
+ * Return the number of RCU batches completed thus far for debug & stats.
+ */
+unsigned long rcu_batches_completed(void)
+{
+ return rcu_state_p->completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
+
+/*
+ * Return the number of RCU-sched batches completed thus far for debug & stats.
+ */
+unsigned long rcu_batches_completed_sched(void)
{
return rcu_sched_state.completed;
}
EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
/*
- * Return the number of RCU BH batches processed thus far for debug & stats.
+ * Return the number of RCU BH batches completed thus far for debug & stats.
*/
-long rcu_batches_completed_bh(void)
+unsigned long rcu_batches_completed_bh(void)
{
return rcu_bh_state.completed;
}
@@ -961,12 +997,6 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp,
}
/*
- * This function really isn't for public consumption, but RCU is special in
- * that context switches can allow the state machine to make progress.
- */
-extern void resched_cpu(int cpu);
-
-/*
* Return true if the specified CPU has passed through a quiescent
* state by virtue of being in or having passed through an dynticks
* idle state since the last call to dyntick_save_progress_counter()
@@ -1151,15 +1181,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
- /*
- * Now rat on any tasks that got kicked up to the root rcu_node
- * due to CPU offlining.
- */
- rnp = rcu_get_root(rsp);
- raw_spin_lock_irqsave(&rnp->lock, flags);
- ndetected += rcu_print_task_stall(rnp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-
print_cpu_stall_info_end();
for_each_possible_cpu(cpu)
totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
@@ -2303,6 +2324,46 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
}
/*
+ * All CPUs for the specified rcu_node structure have gone offline,
+ * and all tasks that were preempted within an RCU read-side critical
+ * section while running on one of those CPUs have since exited their RCU
+ * read-side critical section. Some other CPU is reporting this fact with
+ * the specified rcu_node structure's ->lock held and interrupts disabled.
+ * This function therefore goes up the tree of rcu_node structures,
+ * clearing the corresponding bits in the ->qsmaskinit fields. Note that
+ * the leaf rcu_node structure's ->qsmaskinit field has already been
+ * updated
+ *
+ * This function does check that the specified rcu_node structure has
+ * all CPUs offline and no blocked tasks, so it is OK to invoke it
+ * prematurely. That said, invoking it after the fact will cost you
+ * a needless lock acquisition. So once it has done its work, don't
+ * invoke it again.
+ */
+static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
+{
+ long mask;
+ struct rcu_node *rnp = rnp_leaf;
+
+ if (rnp->qsmaskinit || rcu_preempt_has_tasks(rnp))
+ return;
+ for (;;) {
+ mask = rnp->grpmask;
+ rnp = rnp->parent;
+ if (!rnp)
+ break;
+ raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+ smp_mb__after_unlock_lock(); /* GP memory ordering. */
+ rnp->qsmaskinit &= ~mask;
+ if (rnp->qsmaskinit) {
+ raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ return;
+ }
+ raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ }
+}
+
+/*
* The CPU has been completely removed, and some other CPU is reporting
* this fact from process context. Do the remainder of the cleanup,
* including orphaning the outgoing CPU's RCU callbacks, and also
@@ -2312,8 +2373,6 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
- unsigned long mask;
- int need_report = 0;
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
@@ -2327,40 +2386,15 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
rcu_adopt_orphan_cbs(rsp, flags);
+ raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);
- /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
- mask = rdp->grpmask; /* rnp->grplo is constant. */
- do {
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- smp_mb__after_unlock_lock();
- rnp->qsmaskinit &= ~mask;
- if (rnp->qsmaskinit != 0) {
- if (rnp != rdp->mynode)
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- break;
- }
- if (rnp == rdp->mynode)
- need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
- else
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- mask = rnp->grpmask;
- rnp = rnp->parent;
- } while (rnp != NULL);
-
- /*
- * 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 ->orphan_lock
- * held leads to deadlock.
- */
- raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
- rnp = rdp->mynode;
- if (need_report & RCU_OFL_TASKS_NORM_GP)
- rcu_report_unblock_qs_rnp(rnp, flags);
- else
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- if (need_report & RCU_OFL_TASKS_EXP_GP)
- rcu_report_exp_rnp(rsp, rnp, true);
+ /* Remove outgoing CPU from mask in the leaf rcu_node structure. */
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock(); /* Enforce GP memory-order guarantee. */
+ rnp->qsmaskinit &= ~rdp->grpmask;
+ if (rnp->qsmaskinit == 0 && !rcu_preempt_has_tasks(rnp))
+ rcu_cleanup_dead_rnp(rnp);
+ rcu_report_qs_rnp(rdp->grpmask, rsp, rnp, flags); /* Rlses rnp->lock. */
WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
cpu, rdp->qlen, rdp->nxtlist);
@@ -2376,6 +2410,10 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
{
}
+static void __maybe_unused rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
+{
+}
+
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
}
@@ -2572,12 +2610,6 @@ static void force_qs_rnp(struct rcu_state *rsp,
}
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
- rnp = rcu_get_root(rsp);
- if (rnp->qsmask == 0) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
- smp_mb__after_unlock_lock();
- rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
- }
}
/*
@@ -2677,7 +2709,7 @@ static void rcu_process_callbacks(struct softirq_action *unused)
* Schedule RCU callback invocation. If the specified type 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 interrupts disabled, the
+ * are running on the current CPU with softirqs disabled, the
* rcu_cpu_kthread_task cannot disappear out from under us.
*/
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
@@ -3430,6 +3462,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
} else {
_rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
rsp->n_barrier_done);
+ smp_mb__before_atomic();
atomic_inc(&rsp->barrier_cpu_count);
__call_rcu(&rdp->barrier_head,
rcu_barrier_callback, rsp, cpu, 0);
@@ -3497,9 +3530,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
/* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave(&rnp->lock, flags);
rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
- init_callback_list(rdp);
- rdp->qlen_lazy = 0;
- ACCESS_ONCE(rdp->qlen) = 0;
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 1e7f8b0..119de39 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -27,7 +27,6 @@
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
-#include <linux/irq_work.h>
/*
* Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
@@ -172,11 +171,6 @@ struct rcu_node {
/* queued on this rcu_node structure that */
/* are blocking the current grace period, */
/* there can be no such task. */
- struct completion boost_completion;
- /* Used to ensure that the rt_mutex used */
- /* to carry out the boosting is fully */
- /* released with no future boostee accesses */
- /* before that rt_mutex is re-initialized. */
struct rt_mutex boost_mtx;
/* Used only for the priority-boosting */
/* side effect, not as a lock. */
@@ -343,14 +337,10 @@ struct rcu_data {
#ifdef CONFIG_RCU_NOCB_CPU
struct rcu_head *nocb_head; /* CBs waiting for kthread. */
struct rcu_head **nocb_tail;
- atomic_long_t nocb_q_count; /* # CBs waiting for kthread */
- atomic_long_t nocb_q_count_lazy; /* (approximate). */
+ atomic_long_t nocb_q_count; /* # CBs waiting for nocb */
+ atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */
struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
struct rcu_head **nocb_follower_tail;
- atomic_long_t nocb_follower_count; /* # CBs ready to invoke. */
- atomic_long_t nocb_follower_count_lazy; /* (approximate). */
- int nocb_p_count; /* # CBs being invoked by kthread */
- int nocb_p_count_lazy; /* (approximate). */
wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */
struct task_struct *nocb_kthread;
int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
@@ -359,8 +349,6 @@ struct rcu_data {
struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
/* CBs waiting for GP. */
struct rcu_head **nocb_gp_tail;
- long nocb_gp_count;
- long nocb_gp_count_lazy;
bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */
struct rcu_data *nocb_next_follower;
/* Next follower in wakeup chain. */
@@ -521,13 +509,6 @@ extern struct list_head rcu_struct_flavors;
#define for_each_rcu_flavor(rsp) \
list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
-/* 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. */
-
/*
* RCU implementation internal declarations:
*/
@@ -553,27 +534,16 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
/* Forward declarations for rcutree_plugin.h */
static void rcu_bootup_announce(void);
-long rcu_batches_completed(void);
static void rcu_preempt_note_context_switch(void);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
-static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
- unsigned long flags);
+static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static void rcu_print_detail_task_stall(struct rcu_state *rsp);
static int rcu_print_task_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
-#ifdef CONFIG_HOTPLUG_CPU
-static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
- struct rcu_node *rnp,
- struct rcu_data *rdp);
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
static void rcu_preempt_check_callbacks(void);
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
-#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU)
-static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
- bool wake);
-#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU) */
static void __init __rcu_init_preempt(void);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
@@ -629,24 +599,15 @@ static void rcu_dynticks_task_exit(void);
#endif /* #ifndef RCU_TREE_NONCORE */
#ifdef CONFIG_RCU_TRACE
-#ifdef CONFIG_RCU_NOCB_CPU
-/* Sum up queue lengths for tracing. */
+/* Read out queue lengths for tracing. */
static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
{
- *ql = atomic_long_read(&rdp->nocb_q_count) +
- rdp->nocb_p_count +
- atomic_long_read(&rdp->nocb_follower_count) +
- rdp->nocb_p_count + rdp->nocb_gp_count;
- *qll = atomic_long_read(&rdp->nocb_q_count_lazy) +
- rdp->nocb_p_count_lazy +
- atomic_long_read(&rdp->nocb_follower_count_lazy) +
- rdp->nocb_p_count_lazy + rdp->nocb_gp_count_lazy;
-}
+#ifdef CONFIG_RCU_NOCB_CPU
+ *ql = atomic_long_read(&rdp->nocb_q_count);
+ *qll = atomic_long_read(&rdp->nocb_q_count_lazy);
#else /* #ifdef CONFIG_RCU_NOCB_CPU */
-static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
-{
*ql = 0;
*qll = 0;
-}
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
+}
#endif /* #ifdef CONFIG_RCU_TRACE */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index dcb3263..2e850a5 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -99,6 +99,8 @@ RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
static struct rcu_state *rcu_state_p = &rcu_preempt_state;
static int rcu_preempted_readers_exp(struct rcu_node *rnp);
+static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
+ bool wake);
/*
* Tell them what RCU they are running.
@@ -110,25 +112,6 @@ static void __init rcu_bootup_announce(void)
}
/*
- * Return the number of RCU-preempt batches processed thus far
- * for debug and statistics.
- */
-static long rcu_batches_completed_preempt(void)
-{
- return rcu_preempt_state.completed;
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt);
-
-/*
- * Return the number of RCU batches processed thus far for debug & stats.
- */
-long rcu_batches_completed(void)
-{
- return rcu_batches_completed_preempt();
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed);
-
-/*
* Record a preemptible-RCU quiescent state for the specified CPU. Note
* that this just means that the task currently running on the CPU is
* not in a quiescent state. There might be any number of tasks blocked
@@ -303,15 +286,25 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t,
}
/*
+ * Return true if the specified rcu_node structure has tasks that were
+ * preempted within an RCU read-side critical section.
+ */
+static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
+{
+ return !list_empty(&rnp->blkd_tasks);
+}
+
+/*
* 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.
*/
void rcu_read_unlock_special(struct task_struct *t)
{
- int empty;
- int empty_exp;
- int empty_exp_now;
+ bool empty;
+ bool empty_exp;
+ bool empty_norm;
+ bool empty_exp_now;
unsigned long flags;
struct list_head *np;
#ifdef CONFIG_RCU_BOOST
@@ -363,7 +356,8 @@ void rcu_read_unlock_special(struct task_struct *t)
break;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
- empty = !rcu_preempt_blocked_readers_cgp(rnp);
+ empty = !rcu_preempt_has_tasks(rnp);
+ empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);
empty_exp = !rcu_preempted_readers_exp(rnp);
smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
np = rcu_next_node_entry(t, rnp);
@@ -383,13 +377,21 @@ void rcu_read_unlock_special(struct task_struct *t)
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
+ * If this was the last task on the list, go see if we
+ * need to propagate ->qsmaskinit bit clearing up the
+ * rcu_node tree.
+ */
+ if (!empty && !rcu_preempt_has_tasks(rnp))
+ rcu_cleanup_dead_rnp(rnp);
+
+ /*
* 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 rcu_report_unblock_qs_rnp() releases rnp->lock,
* so we must take a snapshot of the expedited state.
*/
empty_exp_now = !rcu_preempted_readers_exp(rnp);
- if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) {
+ if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) {
trace_rcu_quiescent_state_report(TPS("preempt_rcu"),
rnp->gpnum,
0, rnp->qsmask,
@@ -404,10 +406,8 @@ void rcu_read_unlock_special(struct task_struct *t)
#ifdef CONFIG_RCU_BOOST
/* Unboost if we were boosted. */
- if (drop_boost_mutex) {
+ if (drop_boost_mutex)
rt_mutex_unlock(&rnp->boost_mtx);
- complete(&rnp->boost_completion);
- }
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
@@ -515,99 +515,13 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
{
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
- if (!list_empty(&rnp->blkd_tasks))
+ if (rcu_preempt_has_tasks(rnp))
rnp->gp_tasks = rnp->blkd_tasks.next;
WARN_ON_ONCE(rnp->qsmask);
}
#ifdef CONFIG_HOTPLUG_CPU
-/*
- * Handle tasklist migration for case in which all CPUs covered by the
- * specified rcu_node have gone offline. Move them up to the root
- * 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.
- *
- * The caller must hold rnp->lock with irqs disabled.
- */
-static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
- struct rcu_node *rnp,
- struct rcu_data *rdp)
-{
- struct list_head *lp;
- struct list_head *lp_root;
- int retval = 0;
- struct rcu_node *rnp_root = rcu_get_root(rsp);
- struct task_struct *t;
-
- if (rnp == rnp_root) {
- WARN_ONCE(1, "Last CPU thought to be offlined?");
- return 0; /* Shouldn't happen: at least one CPU online. */
- }
-
- /* If we are on an internal node, complain bitterly. */
- WARN_ON_ONCE(rnp != rdp->mynode);
-
- /*
- * Move tasks up to root rcu_node. Don't try to get fancy for
- * this corner-case operation -- just put this node's tasks
- * at the head of the root node's list, and update the root node's
- * ->gp_tasks and ->exp_tasks pointers to those of this node's,
- * if non-NULL. This might result in waiting for more tasks than
- * absolutely necessary, but this is a good performance/complexity
- * tradeoff.
- */
- if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0)
- retval |= RCU_OFL_TASKS_NORM_GP;
- if (rcu_preempted_readers_exp(rnp))
- retval |= RCU_OFL_TASKS_EXP_GP;
- lp = &rnp->blkd_tasks;
- lp_root = &rnp_root->blkd_tasks;
- while (!list_empty(lp)) {
- t = list_entry(lp->next, typeof(*t), rcu_node_entry);
- raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
- smp_mb__after_unlock_lock();
- list_del(&t->rcu_node_entry);
- t->rcu_blocked_node = rnp_root;
- list_add(&t->rcu_node_entry, lp_root);
- if (&t->rcu_node_entry == rnp->gp_tasks)
- rnp_root->gp_tasks = rnp->gp_tasks;
- if (&t->rcu_node_entry == rnp->exp_tasks)
- rnp_root->exp_tasks = rnp->exp_tasks;
-#ifdef CONFIG_RCU_BOOST
- if (&t->rcu_node_entry == rnp->boost_tasks)
- rnp_root->boost_tasks = rnp->boost_tasks;
-#endif /* #ifdef CONFIG_RCU_BOOST */
- raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
- }
-
- rnp->gp_tasks = NULL;
- rnp->exp_tasks = NULL;
-#ifdef CONFIG_RCU_BOOST
- rnp->boost_tasks = NULL;
- /*
- * In case root is being boosted and leaf was not. Make sure
- * that we boost the tasks blocking the current grace period
- * in this case.
- */
- raw_spin_lock(&rnp_root->lock); /* irqs already disabled */
- smp_mb__after_unlock_lock();
- if (rnp_root->boost_tasks != NULL &&
- rnp_root->boost_tasks != rnp_root->gp_tasks &&
- rnp_root->boost_tasks != rnp_root->exp_tasks)
- rnp_root->boost_tasks = rnp_root->gp_tasks;
- raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
- return retval;
-}
-
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
/*
@@ -767,7 +681,7 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
- if (list_empty(&rnp->blkd_tasks)) {
+ if (!rcu_preempt_has_tasks(rnp)) {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
} else {
rnp->exp_tasks = rnp->blkd_tasks.next;
@@ -929,15 +843,6 @@ static void __init rcu_bootup_announce(void)
}
/*
- * Return the number of RCU batches processed thus far for debug & stats.
- */
-long rcu_batches_completed(void)
-{
- return rcu_batches_completed_sched();
-}
-EXPORT_SYMBOL_GPL(rcu_batches_completed);
-
-/*
* Because preemptible RCU does not exist, we never have to check for
* CPUs being in quiescent states.
*/
@@ -956,11 +861,12 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
#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)
- __releases(rnp->lock)
+/*
+ * Because there is no preemptible RCU, there can be no readers blocked.
+ */
+static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
{
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ return false;
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
@@ -992,23 +898,6 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
WARN_ON_ONCE(rnp->qsmask);
}
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Because preemptible RCU does not exist, it never needs to migrate
- * tasks that were blocked within RCU read-side critical sections, and
- * such non-existent tasks cannot possibly have been blocking the current
- * grace period.
- */
-static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
- struct rcu_node *rnp,
- struct rcu_data *rdp)
-{
- return 0;
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
/*
* Because preemptible RCU does not exist, it never has any callbacks
* to check.
@@ -1027,20 +916,6 @@ void synchronize_rcu_expedited(void)
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-#ifdef CONFIG_HOTPLUG_CPU
-
-/*
- * Because preemptible 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,
- bool wake)
-{
-}
-
-#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-
/*
* Because preemptible RCU does not exist, rcu_barrier() is just
* another name for rcu_barrier_sched().
@@ -1076,7 +951,7 @@ void exit_rcu(void)
static void rcu_initiate_boost_trace(struct rcu_node *rnp)
{
- if (list_empty(&rnp->blkd_tasks))
+ if (!rcu_preempt_has_tasks(rnp))
rnp->n_balk_blkd_tasks++;
else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL)
rnp->n_balk_exp_gp_tasks++;
@@ -1123,7 +998,8 @@ static int rcu_boost(struct rcu_node *rnp)
struct task_struct *t;
struct list_head *tb;
- if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL)
+ if (ACCESS_ONCE(rnp->exp_tasks) == NULL &&
+ ACCESS_ONCE(rnp->boost_tasks) == NULL)
return 0; /* Nothing left to boost. */
raw_spin_lock_irqsave(&rnp->lock, flags);
@@ -1171,15 +1047,11 @@ static int rcu_boost(struct rcu_node *rnp)
*/
t = container_of(tb, struct task_struct, rcu_node_entry);
rt_mutex_init_proxy_locked(&rnp->boost_mtx, t);
- init_completion(&rnp->boost_completion);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
/* Lock only for side effect: boosts task t's priority. */
rt_mutex_lock(&rnp->boost_mtx);
rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */
- /* Wait for boostee to be done w/boost_mtx before reinitializing. */
- wait_for_completion(&rnp->boost_completion);
-
return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
ACCESS_ONCE(rnp->boost_tasks) != NULL;
}
@@ -1412,12 +1284,8 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
if ((mask & 0x1) && cpu != outgoingcpu)
cpumask_set_cpu(cpu, cm);
- if (cpumask_weight(cm) == 0) {
+ if (cpumask_weight(cm) == 0)
cpumask_setall(cm);
- for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
- cpumask_clear_cpu(cpu, cm);
- WARN_ON_ONCE(cpumask_weight(cm) == 0);
- }
set_cpus_allowed_ptr(t, cm);
free_cpumask_var(cm);
}
@@ -1442,12 +1310,8 @@ static void __init rcu_spawn_boost_kthreads(void)
for_each_possible_cpu(cpu)
per_cpu(rcu_cpu_has_work, cpu) = 0;
BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
- rnp = rcu_get_root(rcu_state_p);
- (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
- if (NUM_RCU_NODES > 1) {
- rcu_for_each_leaf_node(rcu_state_p, rnp)
- (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
- }
+ rcu_for_each_leaf_node(rcu_state_p, rnp)
+ (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp);
}
static void rcu_prepare_kthreads(int cpu)
@@ -2054,9 +1918,26 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force)
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
{
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+ unsigned long ret;
+#ifdef CONFIG_PROVE_RCU
struct rcu_head *rhp;
+#endif /* #ifdef CONFIG_PROVE_RCU */
- /* No-CBs CPUs might have callbacks on any of three lists. */
+ /*
+ * Check count of all no-CBs callbacks awaiting invocation.
+ * There needs to be a barrier before this function is called,
+ * but associated with a prior determination that no more
+ * callbacks would be posted. In the worst case, the first
+ * barrier in _rcu_barrier() suffices (but the caller cannot
+ * necessarily rely on this, not a substitute for the caller
+ * getting the concurrency design right!). There must also be
+ * a barrier between the following load an posting of a callback
+ * (if a callback is in fact needed). This is associated with an
+ * atomic_inc() in the caller.
+ */
+ ret = atomic_long_read(&rdp->nocb_q_count);
+
+#ifdef CONFIG_PROVE_RCU
rhp = ACCESS_ONCE(rdp->nocb_head);
if (!rhp)
rhp = ACCESS_ONCE(rdp->nocb_gp_head);
@@ -2070,8 +1951,9 @@ static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
cpu, rhp->func);
WARN_ON_ONCE(1);
}
+#endif /* #ifdef CONFIG_PROVE_RCU */
- return !!rhp;
+ return !!ret;
}
/*
@@ -2093,9 +1975,10 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp,
struct task_struct *t;
/* Enqueue the callback on the nocb list and update counts. */
+ atomic_long_add(rhcount, &rdp->nocb_q_count);
+ /* rcu_barrier() relies on ->nocb_q_count add before xchg. */
old_rhpp = xchg(&rdp->nocb_tail, rhtp);
ACCESS_ONCE(*old_rhpp) = rhp;
- atomic_long_add(rhcount, &rdp->nocb_q_count);
atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy);
smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */
@@ -2286,9 +2169,6 @@ wait_again:
/* Move callbacks to wait-for-GP list, which is empty. */
ACCESS_ONCE(rdp->nocb_head) = NULL;
rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head);
- rdp->nocb_gp_count = atomic_long_xchg(&rdp->nocb_q_count, 0);
- rdp->nocb_gp_count_lazy =
- atomic_long_xchg(&rdp->nocb_q_count_lazy, 0);
gotcbs = true;
}
@@ -2336,9 +2216,6 @@ wait_again:
/* Append callbacks to follower's "done" list. */
tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail);
*tail = rdp->nocb_gp_head;
- atomic_long_add(rdp->nocb_gp_count, &rdp->nocb_follower_count);
- atomic_long_add(rdp->nocb_gp_count_lazy,
- &rdp->nocb_follower_count_lazy);
smp_mb__after_atomic(); /* Store *tail before wakeup. */
if (rdp != my_rdp && tail == &rdp->nocb_follower_head) {
/*
@@ -2413,13 +2290,11 @@ static int rcu_nocb_kthread(void *arg)
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty");
ACCESS_ONCE(rdp->nocb_follower_head) = NULL;
tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head);
- c = atomic_long_xchg(&rdp->nocb_follower_count, 0);
- cl = atomic_long_xchg(&rdp->nocb_follower_count_lazy, 0);
- rdp->nocb_p_count += c;
- rdp->nocb_p_count_lazy += cl;
/* Each pass through the following loop invokes a callback. */
- trace_rcu_batch_start(rdp->rsp->name, cl, c, -1);
+ trace_rcu_batch_start(rdp->rsp->name,
+ atomic_long_read(&rdp->nocb_q_count_lazy),
+ atomic_long_read(&rdp->nocb_q_count), -1);
c = cl = 0;
while (list) {
next = list->next;
@@ -2441,9 +2316,9 @@ static int rcu_nocb_kthread(void *arg)
list = next;
}
trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1);
- ACCESS_ONCE(rdp->nocb_p_count) = rdp->nocb_p_count - c;
- ACCESS_ONCE(rdp->nocb_p_count_lazy) =
- rdp->nocb_p_count_lazy - cl;
+ smp_mb__before_atomic(); /* _add after CB invocation. */
+ atomic_long_add(-c, &rdp->nocb_q_count);
+ atomic_long_add(-cl, &rdp->nocb_q_count_lazy);
rdp->n_nocbs_invoked += c;
}
return 0;
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