sched,lockdep: Employ lock pinning
Employ the new lockdep lock pinning annotation to ensure no
'accidental' lock-breaks happen with rq->lock.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: oleg@redhat.com
Cc: wanpeng.li@linux.intel.com
Cc: umgwanakikbuti@gmail.com
Link: http://lkml.kernel.org/r/20150611124744.003233193@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1ddc129..c74191a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1201,8 +1201,15 @@
stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
tlb_migrate_finish(p->mm);
return 0;
- } else if (task_on_rq_queued(p))
+ } else if (task_on_rq_queued(p)) {
+ /*
+ * OK, since we're going to drop the lock immediately
+ * afterwards anyway.
+ */
+ lockdep_unpin_lock(&rq->lock);
rq = move_queued_task(rq, p, dest_cpu);
+ lockdep_pin_lock(&rq->lock);
+ }
out:
task_rq_unlock(rq, p, &flags);
@@ -1562,6 +1569,8 @@
static inline
int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
{
+ lockdep_assert_held(&p->pi_lock);
+
if (p->nr_cpus_allowed > 1)
cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
@@ -1652,9 +1661,12 @@
#ifdef CONFIG_SMP
if (p->sched_class->task_woken) {
/*
- * XXX can drop rq->lock; most likely ok.
+ * Our task @p is fully woken up and running; so its safe to
+ * drop the rq->lock, hereafter rq is only used for statistics.
*/
+ lockdep_unpin_lock(&rq->lock);
p->sched_class->task_woken(rq, p);
+ lockdep_pin_lock(&rq->lock);
}
if (rq->idle_stamp) {
@@ -1674,6 +1686,8 @@
static void
ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)
{
+ lockdep_assert_held(&rq->lock);
+
#ifdef CONFIG_SMP
if (p->sched_contributes_to_load)
rq->nr_uninterruptible--;
@@ -1718,6 +1732,7 @@
return;
raw_spin_lock_irqsave(&rq->lock, flags);
+ lockdep_pin_lock(&rq->lock);
while (llist) {
p = llist_entry(llist, struct task_struct, wake_entry);
@@ -1725,6 +1740,7 @@
ttwu_do_activate(rq, p, 0);
}
+ lockdep_unpin_lock(&rq->lock);
raw_spin_unlock_irqrestore(&rq->lock, flags);
}
@@ -1821,7 +1837,9 @@
#endif
raw_spin_lock(&rq->lock);
+ lockdep_pin_lock(&rq->lock);
ttwu_do_activate(rq, p, 0);
+ lockdep_unpin_lock(&rq->lock);
raw_spin_unlock(&rq->lock);
}
@@ -1916,9 +1934,17 @@
lockdep_assert_held(&rq->lock);
if (!raw_spin_trylock(&p->pi_lock)) {
+ /*
+ * This is OK, because current is on_cpu, which avoids it being
+ * picked for load-balance and preemption/IRQs are still
+ * disabled avoiding further scheduler activity on it and we've
+ * not yet picked a replacement task.
+ */
+ lockdep_unpin_lock(&rq->lock);
raw_spin_unlock(&rq->lock);
raw_spin_lock(&p->pi_lock);
raw_spin_lock(&rq->lock);
+ lockdep_pin_lock(&rq->lock);
}
if (!(p->state & TASK_NORMAL))
@@ -2530,6 +2556,7 @@
* of the scheduler it's an obvious special-case), so we
* do an early lockdep release here:
*/
+ lockdep_unpin_lock(&rq->lock);
spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
context_tracking_task_switch(prev, next);
@@ -2953,6 +2980,7 @@
*/
smp_mb__before_spinlock();
raw_spin_lock_irq(&rq->lock);
+ lockdep_pin_lock(&rq->lock);
rq->clock_skip_update <<= 1; /* promote REQ to ACT */
@@ -2995,8 +3023,10 @@
rq = context_switch(rq, prev, next); /* unlocks the rq */
cpu = cpu_of(rq);
- } else
+ } else {
+ lockdep_unpin_lock(&rq->lock);
raw_spin_unlock_irq(&rq->lock);
+ }
balance_callback(rq);
}
@@ -5065,6 +5095,11 @@
if (rq->nr_running == 1)
break;
+ /*
+ * Ensure rq->lock covers the entire task selection
+ * until the migration.
+ */
+ lockdep_pin_lock(&rq->lock);
next = pick_next_task(rq, &fake_task);
BUG_ON(!next);
next->sched_class->put_prev_task(rq, next);
@@ -5072,6 +5107,7 @@
/* Find suitable destination for @next, with force if needed. */
dest_cpu = select_fallback_rq(dead_rq->cpu, next);
+ lockdep_unpin_lock(&rq->lock);
rq = __migrate_task(rq, next, dest_cpu);
if (rq != dead_rq) {
raw_spin_unlock(&rq->lock);
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 6318f43..e814641 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1151,7 +1151,15 @@
dl_rq = &rq->dl;
if (need_pull_dl_task(rq, prev)) {
+ /*
+ * This is OK, because current is on_cpu, which avoids it being
+ * picked for load-balance and preemption/IRQs are still
+ * disabled avoiding further scheduler activity on it and we're
+ * being very careful to re-start the picking loop.
+ */
+ lockdep_unpin_lock(&rq->lock);
pull_dl_task(rq);
+ lockdep_pin_lock(&rq->lock);
/*
* pull_rt_task() can drop (and re-acquire) rq->lock; this
* means a stop task can slip in, in which case we need to
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7210ae8..509ef63 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5392,7 +5392,15 @@
return p;
idle:
+ /*
+ * This is OK, because current is on_cpu, which avoids it being picked
+ * for load-balance and preemption/IRQs are still disabled avoiding
+ * further scheduler activity on it and we're being very careful to
+ * re-start the picking loop.
+ */
+ lockdep_unpin_lock(&rq->lock);
new_tasks = idle_balance(rq);
+ lockdep_pin_lock(&rq->lock);
/*
* Because idle_balance() releases (and re-acquires) rq->lock, it is
* possible for any higher priority task to appear. In that case we
@@ -7426,9 +7434,6 @@
goto out;
}
- /*
- * Drop the rq->lock, but keep IRQ/preempt disabled.
- */
raw_spin_unlock(&this_rq->lock);
update_blocked_averages(this_cpu);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 460f858..0d193a24 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1478,7 +1478,15 @@
struct rt_rq *rt_rq = &rq->rt;
if (need_pull_rt_task(rq, prev)) {
+ /*
+ * This is OK, because current is on_cpu, which avoids it being
+ * picked for load-balance and preemption/IRQs are still
+ * disabled avoiding further scheduler activity on it and we're
+ * being very careful to re-start the picking loop.
+ */
+ lockdep_unpin_lock(&rq->lock);
pull_rt_task(rq);
+ lockdep_pin_lock(&rq->lock);
/*
* pull_rt_task() can drop (and re-acquire) rq->lock; this
* means a dl or stop task can slip in, in which case we need
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 62949ab..ef02d11 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1439,8 +1439,10 @@
for (;;) {
rq = task_rq(p);
raw_spin_lock(&rq->lock);
- if (likely(rq == task_rq(p) && !task_on_rq_migrating(p)))
+ if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
+ lockdep_pin_lock(&rq->lock);
return rq;
+ }
raw_spin_unlock(&rq->lock);
while (unlikely(task_on_rq_migrating(p)))
@@ -1477,8 +1479,10 @@
* If we observe the new cpu in task_rq_lock, the acquire will
* pair with the WMB to ensure we must then also see migrating.
*/
- if (likely(rq == task_rq(p) && !task_on_rq_migrating(p)))
+ if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
+ lockdep_pin_lock(&rq->lock);
return rq;
+ }
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
@@ -1490,6 +1494,7 @@
static inline void __task_rq_unlock(struct rq *rq)
__releases(rq->lock)
{
+ lockdep_unpin_lock(&rq->lock);
raw_spin_unlock(&rq->lock);
}
@@ -1498,6 +1503,7 @@
__releases(rq->lock)
__releases(p->pi_lock)
{
+ lockdep_unpin_lock(&rq->lock);
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
}