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Revert "perf/aux: Fix AUX buffer serialization"

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This reverts commit c4b69bee3f which is
commit 2ab9d83026 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 (hint, it will be...)

Bug: 161946584
Change-Id: Ib2b142635750c4b2f88432b7cccb4ed971b1c70d
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman 2024-09-12 12:58:30 +00:00
parent d16ed636ab
commit e7a4f5e3ae
3 changed files with 6 additions and 15 deletions
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18
kernel/events/core.c
View File

@ -1255,9 +1255,8 @@ 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
@ -6331,11 +6330,12 @@ 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
@ -6352,7 +6352,7 @@ 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))
@ -6440,7 +6440,6 @@ 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;
@ -6489,9 +6488,6 @@ 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);
@ -6642,8 +6638,6 @@ unlock:
atomic_dec(&rb->mmap_count);
}
aux_unlock:
if (aux_mutex)
mutex_unlock(aux_mutex);
mutex_unlock(&event->mmap_mutex);
/*

1
kernel/events/internal.h
View File

@ -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 */

2
kernel/events/ring_buffer.c
View File

@ -333,8 +333,6 @@ 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)