Commit de506eec authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'perf_urgent_for_v6.2_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull perf fix from Borislav Petkov:

 - Lock the proper critical section when dealing with perf event context

* tag 'perf_urgent_for_v6.2_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf: Fix perf_event_pmu_context serialization
parents 837c07cf 4f64a6c9

include/linux/spinlock.h

+9 −0
Original line number Diff line number Diff line
@@ -476,6 +476,15 @@ extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, 
#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \

		__cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))



extern int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock);

#define atomic_dec_and_raw_lock(atomic, lock) \

		__cond_lock(lock, _atomic_dec_and_raw_lock(atomic, lock))



extern int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,

					unsigned long *flags);

#define atomic_dec_and_raw_lock_irqsave(atomic, lock, flags) \

		__cond_lock(lock, _atomic_dec_and_raw_lock_irqsave(atomic, lock, &(flags)))



int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,

			     size_t max_size, unsigned int cpu_mult,

			     gfp_t gfp, const char *name,

kernel/events/core.c

+17 −22
Original line number Diff line number Diff line
@@ -4813,19 +4813,17 @@ find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx, 


		cpc = per_cpu_ptr(pmu->cpu_pmu_context, event->cpu);

		epc = &cpc->epc;



		raw_spin_lock_irq(&ctx->lock);

		if (!epc->ctx) {

			atomic_set(&epc->refcount, 1);

			epc->embedded = 1;

			raw_spin_lock_irq(&ctx->lock);

			list_add(&epc->pmu_ctx_entry, &ctx->pmu_ctx_list);

			epc->ctx = ctx;

			raw_spin_unlock_irq(&ctx->lock);

		} else {

			WARN_ON_ONCE(epc->ctx != ctx);

			atomic_inc(&epc->refcount);

		}



		raw_spin_unlock_irq(&ctx->lock);

		return epc;

	}
@@ -4896,13 +4894,8 @@ static void free_epc_rcu(struct rcu_head *head) 


static void put_pmu_ctx(struct perf_event_pmu_context *epc)

{

	unsigned long flags;



	if (!atomic_dec_and_test(&epc->refcount))

		return;



	if (epc->ctx) {

	struct perf_event_context *ctx = epc->ctx;

	unsigned long flags;



	/*

	 * XXX
@@ -4912,17 +4905,19 @@ static void put_pmu_ctx(struct perf_event_pmu_context *epc) 
	 * can't because of the call-site in _free_event()/put_event()

	 * which isn't always called under ctx->mutex.

	 */

	if (!atomic_dec_and_raw_lock_irqsave(&epc->refcount, &ctx->lock, flags))

		return;



	WARN_ON_ONCE(list_empty(&epc->pmu_ctx_entry));

		raw_spin_lock_irqsave(&ctx->lock, flags);



	list_del_init(&epc->pmu_ctx_entry);

	epc->ctx = NULL;

		raw_spin_unlock_irqrestore(&ctx->lock, flags);

	}



	WARN_ON_ONCE(!list_empty(&epc->pinned_active));

	WARN_ON_ONCE(!list_empty(&epc->flexible_active));



	raw_spin_unlock_irqrestore(&ctx->lock, flags);



	if (epc->embedded)

		return;

lib/dec_and_lock.c

+31 −0
Original line number Diff line number Diff line
@@ -49,3 +49,34 @@ int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock, 
	return 0;

}

EXPORT_SYMBOL(_atomic_dec_and_lock_irqsave);



int _atomic_dec_and_raw_lock(atomic_t *atomic, raw_spinlock_t *lock)

{

	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */

	if (atomic_add_unless(atomic, -1, 1))

		return 0;



	/* Otherwise do it the slow way */

	raw_spin_lock(lock);

	if (atomic_dec_and_test(atomic))

		return 1;

	raw_spin_unlock(lock);

	return 0;

}

EXPORT_SYMBOL(_atomic_dec_and_raw_lock);



int _atomic_dec_and_raw_lock_irqsave(atomic_t *atomic, raw_spinlock_t *lock,

				     unsigned long *flags)

{

	/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */

	if (atomic_add_unless(atomic, -1, 1))

		return 0;



	/* Otherwise do it the slow way */

	raw_spin_lock_irqsave(lock, *flags);

	if (atomic_dec_and_test(atomic))

		return 1;

	raw_spin_unlock_irqrestore(lock, *flags);

	return 0;

}

EXPORT_SYMBOL(_atomic_dec_and_raw_lock_irqsave);