From 99de38240fad6115b68ddd63caaad69ef87603a4 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Wed, 2 Oct 2024 09:40:05 +0000 Subject: [PATCH] Revert "perf/aux: Fix AUX buffer serialization" This reverts commit 9dc7ad2b67772cfb94ceb3b0c9c4023c2463215d 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: Id119523c115b8a3aec08978e22bdb4e894701923 Signed-off-by: Greg Kroah-Hartman --- kernel/events/core.c | 18 ++++++------------ kernel/events/internal.h | 1 - kernel/events/ring_buffer.c | 2 -- 3 files changed, 6 insertions(+), 15 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index ec84ea900c76..a92188783ed1 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1277,9 +1277,8 @@ 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 @@ -6158,11 +6157,12 @@ 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 @@ -6179,7 +6179,7 @@ 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)) @@ -6267,7 +6267,6 @@ 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; @@ -6316,9 +6315,6 @@ 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); @@ -6469,8 +6465,6 @@ unlock: 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 f376b057320c..386d21c7edfa 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 98588e96b591..f3a3c294ff2b 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -332,8 +332,6 @@ 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)