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authorPeter Zijlstra <peterz@infradead.org>2018-02-06 17:52:13 +0100
committerIngo Molnar <mingo@kernel.org>2018-02-13 11:44:41 +0100
commit269d599271fa604f09d5cb0093c5dd5d59964dd5 (patch)
treee6cb32acb59211a8842d78f3590ba54165ae8491
parenta7711602c7b79950ea437178f601b52ab08ef659 (diff)
downloadlinux-269d599271fa604f09d5cb0093c5dd5d59964dd5.tar.bz2
sched/core: Fix DEBUG_SPINLOCK annotation for rq->lock
Mark noticed that he had sporadic "spinlock recursion" warnings from the DEBUG_SPINLOCK code. Now rq->lock is special in that the owner changes in the middle of a context switch. It so happens that we fix up the lock.owner too late, @prev can run (remotely) the moment prev->on_cpu is cleared, this then allows @prev to again try and acquire this rq->lock and trigger this warning. So we have to switch lock.owner before clearing prev->on_cpu. Do this by moving the DEBUG_SPINLOCK annotation from after switch_to() to before switch_to() and collect all lockdep annotations there into prepare_lock_switch() to mirror the existing finish_lock_switch(). Debugged-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/sched/core.c27
1 files changed, 16 insertions, 11 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bf724c1952ea..e7c535eee0a6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2601,19 +2601,31 @@ static inline void finish_task(struct task_struct *prev)
#endif
}
-static inline void finish_lock_switch(struct rq *rq)
+static inline void
+prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
{
+ /*
+ * Since the runqueue lock will be released by the next
+ * task (which is an invalid locking op but in the case
+ * of the scheduler it's an obvious special-case), so we
+ * do an early lockdep release here:
+ */
+ rq_unpin_lock(rq, rf);
+ spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
- rq->lock.owner = current;
+ rq->lock.owner = next;
#endif
+}
+
+static inline void finish_lock_switch(struct rq *rq)
+{
/*
* If we are tracking spinlock dependencies then we have to
* fix up the runqueue lock - which gets 'carried over' from
* prev into current:
*/
spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
-
raw_spin_unlock_irq(&rq->lock);
}
@@ -2844,14 +2856,7 @@ context_switch(struct rq *rq, struct task_struct *prev,
rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
- /*
- * Since the runqueue lock will be released by the next
- * task (which is an invalid locking op but in the case
- * of the scheduler it's an obvious special-case), so we
- * do an early lockdep release here:
- */
- rq_unpin_lock(rq, rf);
- spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
+ prepare_lock_switch(rq, next, rf);
/* Here we just switch the register state and the stack. */
switch_to(prev, next, prev);