Revert "perf/aux: Fix AUX buffer serialization"
This reverts commit 52d13d224fdf1299c8b642807fa1ea14d693f5ff which is
commit 2ab9d830262c132ab5db2f571003d80850d56b2a upstream.
It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.
Bug: 161946584
Change-Id: Ia2a0469ba8f50d54ced5d818f36c8d07f977f1a0
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6309226..7e427f1 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1367,9 +1367,8 @@ static void put_ctx(struct perf_event_context *ctx)
* perf_event_context::mutex
* perf_event::child_mutex;
* perf_event_context::lock
+ * perf_event::mmap_mutex
* mmap_lock
- * perf_event::mmap_mutex
- * perf_buffer::aux_mutex
* perf_addr_filters_head::lock
*
* cpu_hotplug_lock
@@ -6207,11 +6206,12 @@ static void perf_mmap_close(struct vm_area_struct *vma)
event->pmu->event_unmapped(event, vma->vm_mm);
/*
- * The AUX buffer is strictly a sub-buffer, serialize using aux_mutex
- * to avoid complications.
+ * rb->aux_mmap_count will always drop before rb->mmap_count and
+ * event->mmap_count, so it is ok to use event->mmap_mutex to
+ * serialize with perf_mmap here.
*/
if (rb_has_aux(rb) && vma->vm_pgoff == rb->aux_pgoff &&
- atomic_dec_and_mutex_lock(&rb->aux_mmap_count, &rb->aux_mutex)) {
+ atomic_dec_and_mutex_lock(&rb->aux_mmap_count, &event->mmap_mutex)) {
/*
* Stop all AUX events that are writing to this buffer,
* so that we can free its AUX pages and corresponding PMU
@@ -6228,7 +6228,7 @@ static void perf_mmap_close(struct vm_area_struct *vma)
rb_free_aux(rb);
WARN_ON_ONCE(refcount_read(&rb->aux_refcount));
- mutex_unlock(&rb->aux_mutex);
+ mutex_unlock(&event->mmap_mutex);
}
if (atomic_dec_and_test(&rb->mmap_count))
@@ -6316,7 +6316,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
struct perf_event *event = file->private_data;
unsigned long user_locked, user_lock_limit;
struct user_struct *user = current_user();
- struct mutex *aux_mutex = NULL;
struct perf_buffer *rb = NULL;
unsigned long locked, lock_limit;
unsigned long vma_size;
@@ -6365,9 +6364,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
if (!rb)
goto aux_unlock;
- aux_mutex = &rb->aux_mutex;
- mutex_lock(aux_mutex);
-
aux_offset = READ_ONCE(rb->user_page->aux_offset);
aux_size = READ_ONCE(rb->user_page->aux_size);
@@ -6518,8 +6514,6 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
atomic_dec(&rb->mmap_count);
}
aux_unlock:
- if (aux_mutex)
- mutex_unlock(aux_mutex);
mutex_unlock(&event->mmap_mutex);
/*
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index f376b057..386d21c 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -40,7 +40,6 @@ struct perf_buffer {
struct user_struct *mmap_user;
/* AUX area */
- struct mutex aux_mutex;
long aux_head;
unsigned int aux_nest;
long aux_wakeup; /* last aux_watermark boundary crossed by aux_head */
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 35b60d9..b5d5aa5 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -329,8 +329,6 @@ ring_buffer_init(struct perf_buffer *rb, long watermark, int flags)
*/
if (!rb->nr_pages)
rb->paused = 1;
-
- mutex_init(&rb->aux_mutex);
}
void perf_aux_output_flag(struct perf_output_handle *handle, u64 flags)
