perf: Fix AUX buffer refcounting
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@ -90,6 +90,7 @@ linux (4.1.6-1) UNRELEASED; urgency=medium
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[ Ben Hutchings ]
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* [i386] udeb: Make gpio_keys_polled and leds-gpio optional in input-modules
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as they are not built for the 686-pae flavour (fixes FTBFS)
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* perf: Fix AUX buffer refcounting
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-- Aurelien Jarno <aurel32@debian.org> Tue, 18 Aug 2015 11:35:05 +0200
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@ -0,0 +1,135 @@
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From: Peter Zijlstra <peterz@infradead.org>
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Date: Thu, 18 Jun 2015 12:32:49 +0200
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Subject: perf: Fix AUX buffer refcounting
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Origin: https://git.kernel.org/linus/57ffc5ca679f499f4704fd9b6a372916f59930ee
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Its currently possible to drop the last refcount to the aux buffer
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from NMI context, which results in the expected fireworks.
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The refcounting needs a bigger overhaul, but to cure the immediate
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problem, delay the freeing by using an irq_work.
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Reviewed-and-tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
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Reported-by: Vince Weaver <vincent.weaver@maine.edu>
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Stephane Eranian <eranian@gmail.com>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Link: http://lkml.kernel.org/r/20150618103249.GK19282@twins.programming.kicks-ass.net
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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---
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kernel/events/core.c | 8 --------
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kernel/events/internal.h | 10 ++++++++++
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kernel/events/ring_buffer.c | 27 +++++++++++++++++++++++++--
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3 files changed, 35 insertions(+), 10 deletions(-)
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--- a/kernel/events/core.c
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+++ b/kernel/events/core.c
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@@ -4381,14 +4381,6 @@ static void ring_buffer_wakeup(struct pe
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rcu_read_unlock();
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}
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-static void rb_free_rcu(struct rcu_head *rcu_head)
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-{
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- struct ring_buffer *rb;
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-
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- rb = container_of(rcu_head, struct ring_buffer, rcu_head);
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- rb_free(rb);
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-}
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-
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struct ring_buffer *ring_buffer_get(struct perf_event *event)
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{
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struct ring_buffer *rb;
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--- a/kernel/events/internal.h
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+++ b/kernel/events/internal.h
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@@ -11,6 +11,7 @@
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struct ring_buffer {
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atomic_t refcount;
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struct rcu_head rcu_head;
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+ struct irq_work irq_work;
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#ifdef CONFIG_PERF_USE_VMALLOC
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struct work_struct work;
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int page_order; /* allocation order */
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@@ -55,6 +56,15 @@ struct ring_buffer {
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};
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extern void rb_free(struct ring_buffer *rb);
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+
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+static inline void rb_free_rcu(struct rcu_head *rcu_head)
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+{
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+ struct ring_buffer *rb;
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+
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+ rb = container_of(rcu_head, struct ring_buffer, rcu_head);
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+ rb_free(rb);
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+}
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+
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extern struct ring_buffer *
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rb_alloc(int nr_pages, long watermark, int cpu, int flags);
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extern void perf_event_wakeup(struct perf_event *event);
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--- a/kernel/events/ring_buffer.c
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+++ b/kernel/events/ring_buffer.c
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@@ -221,6 +221,8 @@ void perf_output_end(struct perf_output_
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rcu_read_unlock();
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}
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+static void rb_irq_work(struct irq_work *work);
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+
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static void
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ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
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{
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@@ -241,6 +243,16 @@ ring_buffer_init(struct ring_buffer *rb,
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INIT_LIST_HEAD(&rb->event_list);
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spin_lock_init(&rb->event_lock);
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+ init_irq_work(&rb->irq_work, rb_irq_work);
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+}
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+
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+static void ring_buffer_put_async(struct ring_buffer *rb)
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+{
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+ if (!atomic_dec_and_test(&rb->refcount))
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+ return;
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+
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+ rb->rcu_head.next = (void *)rb;
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+ irq_work_queue(&rb->irq_work);
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}
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/*
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@@ -319,7 +331,7 @@ err_put:
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rb_free_aux(rb);
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err:
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- ring_buffer_put(rb);
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+ ring_buffer_put_async(rb);
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handle->event = NULL;
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return NULL;
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@@ -370,7 +382,7 @@ void perf_aux_output_end(struct perf_out
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local_set(&rb->aux_nest, 0);
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rb_free_aux(rb);
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- ring_buffer_put(rb);
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+ ring_buffer_put_async(rb);
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}
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/*
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@@ -557,7 +569,18 @@ static void __rb_free_aux(struct ring_bu
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void rb_free_aux(struct ring_buffer *rb)
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{
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if (atomic_dec_and_test(&rb->aux_refcount))
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+ irq_work_queue(&rb->irq_work);
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+}
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+
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+static void rb_irq_work(struct irq_work *work)
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+{
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+ struct ring_buffer *rb = container_of(work, struct ring_buffer, irq_work);
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+
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+ if (!atomic_read(&rb->aux_refcount))
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__rb_free_aux(rb);
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+
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+ if (rb->rcu_head.next == (void *)rb)
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+ call_rcu(&rb->rcu_head, rb_free_rcu);
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}
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#ifndef CONFIG_PERF_USE_VMALLOC
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@ -24,7 +24,7 @@ Signed-off-by: Ingo Molnar <mingo@kernel.org>
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--- a/kernel/events/ring_buffer.c
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+++ b/kernel/events/ring_buffer.c
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@@ -547,11 +547,13 @@ static void __rb_free_aux(struct ring_bu
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@@ -559,11 +559,13 @@ static void __rb_free_aux(struct ring_bu
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rb->aux_priv = NULL;
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}
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@ -90,4 +90,5 @@ bugfix/all/virtio-net-drop-netif_f_fraglist.patch
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bugfix/all/-ovl-don-t-traverse-automount-points.patch
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bugfix/all/ovl-allow-distributed-fs-as-lower-layer.patch
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bugfix/all/fix-a-braino-in-ovl_d_select_inode.patch
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bugfix/all/perf-fix-aux-buffer-refcounting.patch
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bugfix/all/perf-fix-double-free-of-the-aux-buffer.patch
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