From 57ffc5ca679f499f4704fd9b6a372916f59930ee Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 18 Jun 2015 12:32:49 +0200 Subject: perf: Fix AUX buffer refcounting Its currently possible to drop the last refcount to the aux buffer from NMI context, which results in the expected fireworks. The refcounting needs a bigger overhaul, but to cure the immediate problem, delay the freeing by using an irq_work. Reviewed-and-tested-by: Alexander Shishkin Reported-by: Vince Weaver Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20150618103249.GK19282@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/events/ring_buffer.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) (limited to 'kernel/events/ring_buffer.c') diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 96472824a752..b2be01b1aa9d 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -221,6 +221,8 @@ void perf_output_end(struct perf_output_handle *handle) rcu_read_unlock(); } +static void rb_irq_work(struct irq_work *work); + static void ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) { @@ -241,6 +243,16 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) INIT_LIST_HEAD(&rb->event_list); spin_lock_init(&rb->event_lock); + init_irq_work(&rb->irq_work, rb_irq_work); +} + +static void ring_buffer_put_async(struct ring_buffer *rb) +{ + if (!atomic_dec_and_test(&rb->refcount)) + return; + + rb->rcu_head.next = (void *)rb; + irq_work_queue(&rb->irq_work); } /* @@ -319,7 +331,7 @@ err_put: rb_free_aux(rb); err: - ring_buffer_put(rb); + ring_buffer_put_async(rb); handle->event = NULL; return NULL; @@ -370,7 +382,7 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size, local_set(&rb->aux_nest, 0); rb_free_aux(rb); - ring_buffer_put(rb); + ring_buffer_put_async(rb); } /* @@ -557,7 +569,18 @@ static void __rb_free_aux(struct ring_buffer *rb) void rb_free_aux(struct ring_buffer *rb) { if (atomic_dec_and_test(&rb->aux_refcount)) + irq_work_queue(&rb->irq_work); +} + +static void rb_irq_work(struct irq_work *work) +{ + struct ring_buffer *rb = container_of(work, struct ring_buffer, irq_work); + + if (!atomic_read(&rb->aux_refcount)) __rb_free_aux(rb); + + if (rb->rcu_head.next == (void *)rb) + call_rcu(&rb->rcu_head, rb_free_rcu); } #ifndef CONFIG_PERF_USE_VMALLOC -- cgit