This patch illustrates the transition to local{,64}_try_cmpxchg.
It is not intended to be merged as-is.
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
---
arch/x86/events/core.c | 9 ++++-----
kernel/events/ring_buffer.c | 5 +++--
2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index d096b04bf80e..d9310e9363f1 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -129,13 +129,12 @@ u64 x86_perf_event_update(struct perf_event *event)
* exchange a new raw count - then add that new-prev delta
* count to the generic event atomically:
*/
-again:
prev_raw_count = local64_read(&hwc->prev_count);
- rdpmcl(hwc->event_base_rdpmc, new_raw_count);
- if (local64_cmpxchg(&hwc->prev_count, prev_raw_count,
- new_raw_count) != prev_raw_count)
- goto again;
+ do {
+ rdpmcl(hwc->event_base_rdpmc, new_raw_count);
+ } while (!local64_try_cmpxchg(&hwc->prev_count, &prev_raw_count,
+ new_raw_count));
/*
* Now we have the new raw value and have updated the prev
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 273a0fe7910a..111ab85ee97d 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -191,9 +191,10 @@ __perf_output_begin(struct perf_output_handle *handle,
perf_output_get_handle(handle);
+ offset = local_read(&rb->head);
do {
tail = READ_ONCE(rb->user_page->data_tail);
- offset = head = local_read(&rb->head);
+ head = offset;
if (!rb->overwrite) {
if (unlikely(!ring_buffer_has_space(head, tail,
perf_data_size(rb),
@@ -217,7 +218,7 @@ __perf_output_begin(struct perf_output_handle *handle,
head += size;
else
head -= size;
- } while (local_cmpxchg(&rb->head, offset, head) != offset);
+ } while (!local_try_cmpxchg(&rb->head, &offset, head));
if (backward) {
offset = head;
--
2.39.2
