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perf: Fix AUX buffer refcounting

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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 <alexander.shishkin@linux.intel.com>
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150618103249.GK19282@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-06-18 12:32:49 +02:00 committed by Ingo Molnar
parent d2d61ed55f
commit 57ffc5ca67
3 changed files with 35 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
kernel/events/core.c
View File

@ -4358,14 +4358,6 @@ static void ring_buffer_wakeup(struct perf_event *event)
rcu_read_unlock();
}
static void rb_free_rcu(struct rcu_head *rcu_head)
{
struct ring_buffer *rb;
rb = container_of(rcu_head, struct ring_buffer, rcu_head);
rb_free(rb);
}
struct ring_buffer *ring_buffer_get(struct perf_event *event)
{
struct ring_buffer *rb;

10
kernel/events/internal.h
View File

@ -11,6 +11,7 @@
struct ring_buffer {
atomic_t refcount;
struct rcu_head rcu_head;
struct irq_work irq_work;
#ifdef CONFIG_PERF_USE_VMALLOC
struct work_struct work;
int page_order; /* allocation order */
@ -55,6 +56,15 @@ struct ring_buffer {
};
extern void rb_free(struct ring_buffer *rb);
static inline void rb_free_rcu(struct rcu_head *rcu_head)
{
struct ring_buffer *rb;
rb = container_of(rcu_head, struct ring_buffer, rcu_head);
rb_free(rb);
}
extern struct ring_buffer *
rb_alloc(int nr_pages, long watermark, int cpu, int flags);
extern void perf_event_wakeup(struct perf_event *event);

27
kernel/events/ring_buffer.c
View File

@ -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