On Tue, Jun 16, 2015 at 02:37:06PM +0300, Alexander Shishkin wrote:
> Ok, here's what I propose for this one.
As discussed yesterday, I think we want to change to how we do reference
counting for the regular buffers, but that will require quite a bit of
work.
For the interim we can avoid the issue by something like the below;
compile tested only.
---
kernel/events/core.c | 8 --------
kernel/events/internal.h | 10 ++++++++++
kernel/events/ring_buffer.c | 27 +++++++++++++++++++++++++--
3 files changed, 35 insertions(+), 10 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1e33b9141f03..76b7694b7909 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4352,14 +4352,6 @@ 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;
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 2deb24c7a40d..2bbad9c1274c 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -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);
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 @@ void *perf_aux_output_begin(struct perf_output_handle
*handle,
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
--
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