The aux_head and aux_wakeup members of struct ring_buffer are defined
using the local_t type, despite the fact that they are only accessed via
the perf_aux_output_* functions, which cannot race with each other for a
given ring buffer.
This patch changes the type of the members to long, so we can avoid
using the local_* API where it isn't needed.
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Will Deacon <will.dea...@arm.com>
---
kernel/events/internal.h | 4 ++--
kernel/events/ring_buffer.c | 27 +++++++++++++--------------
2 files changed, 15 insertions(+), 16 deletions(-)
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 486fd78eb8d5..2941b868353c 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -38,9 +38,9 @@ struct ring_buffer {
struct user_struct *mmap_user;
/* AUX area */
- local_t aux_head;
+ long aux_head;
local_t aux_nest;
- local_t aux_wakeup;
+ long aux_wakeup;
unsigned long aux_pgoff;
int aux_nr_pages;
int aux_overwrite;
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 14a240ff439d..330df5a7f762 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -367,7 +367,7 @@ void *perf_aux_output_begin(struct perf_output_handle
*handle,
if (WARN_ON_ONCE(local_xchg(&rb->aux_nest, 1)))
goto err_put;
- aux_head = local_read(&rb->aux_head);
+ aux_head = rb->aux_head;
handle->rb = rb;
handle->event = event;
@@ -382,7 +382,7 @@ void *perf_aux_output_begin(struct perf_output_handle
*handle,
*/
if (!rb->aux_overwrite) {
aux_tail = ACCESS_ONCE(rb->user_page->aux_tail);
- handle->wakeup = local_read(&rb->aux_wakeup) +
rb->aux_watermark;
+ handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
if (aux_head - aux_tail < perf_aux_size(rb))
handle->size = CIRC_SPACE(aux_head, aux_tail,
perf_aux_size(rb));
@@ -434,12 +434,12 @@ void perf_aux_output_end(struct perf_output_handle
*handle, unsigned long size)
handle->aux_flags |= PERF_AUX_FLAG_OVERWRITE;
aux_head = handle->head;
- local_set(&rb->aux_head, aux_head);
+ rb->aux_head = aux_head;
} else {
handle->aux_flags &= ~PERF_AUX_FLAG_OVERWRITE;
- aux_head = local_read(&rb->aux_head);
- local_add(size, &rb->aux_head);
+ aux_head = rb->aux_head;
+ rb->aux_head += size;
}
if (size || handle->aux_flags) {
@@ -451,11 +451,11 @@ void perf_aux_output_end(struct perf_output_handle
*handle, unsigned long size)
handle->aux_flags);
}
- aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
+ aux_head = rb->user_page->aux_head = rb->aux_head;
- if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ if (aux_head - rb->aux_wakeup >= rb->aux_watermark) {
wakeup = true;
- local_add(rb->aux_watermark, &rb->aux_wakeup);
+ rb->aux_wakeup += rb->aux_watermark;
}
if (wakeup) {
@@ -485,14 +485,13 @@ int perf_aux_output_skip(struct perf_output_handle
*handle, unsigned long size)
if (size > handle->size)
return -ENOSPC;
- local_add(size, &rb->aux_head);
+ rb->aux_head += size;
- aux_head = rb->user_page->aux_head = local_read(&rb->aux_head);
- if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) {
+ aux_head = rb->user_page->aux_head = rb->aux_head;
+ if (aux_head - rb->aux_wakeup >= rb->aux_watermark) {
perf_output_wakeup(handle);
- local_add(rb->aux_watermark, &rb->aux_wakeup);
- handle->wakeup = local_read(&rb->aux_wakeup) +
- rb->aux_watermark;
+ rb->aux_wakeup += rb->aux_watermark;
+ handle->wakeup = rb->aux_wakeup + rb->aux_watermark;
}
handle->head = aux_head;
--
2.1.4
