From: Uros Bizjak <ubizjak@gmail.com>
To: linux-alpha@vger.kernel.org, loongarch@lists.linux.dev,
linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
x86@kernel.org, linux-arch@vger.kernel.org,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>
Subject: [PATCH v2 5/5] events: Illustrate the transition to local{,64}_try_cmpxchg
Date: Wed, 5 Apr 2023 16:17:10 +0200 [thread overview]
Message-ID: <20230405141710.3551-6-ubizjak@gmail.com> (raw)
In-Reply-To: <20230405141710.3551-1-ubizjak@gmail.com>
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@gmail.com>
---
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
next prev parent reply other threads:[~2023-04-05 14:17 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-05 14:17 [PATCH v2 0/5] locking: Introduce local{,64}_try_cmpxchg Uros Bizjak
2023-04-05 14:17 ` [PATCH v2 1/5] locking/atomic: Add generic try_cmpxchg{,64}_local support Uros Bizjak
2023-04-11 11:10 ` Mark Rutland
2023-04-05 14:17 ` [PATCH v2 2/5] locking/generic: Wire up local{,64}_try_cmpxchg Uros Bizjak
2023-04-11 11:13 ` Mark Rutland
2023-04-05 14:17 ` [PATCH v2 3/5] locking/arch: Wire up local_try_cmpxchg Uros Bizjak
2023-04-12 11:32 ` Peter Zijlstra
2023-04-12 13:37 ` Uros Bizjak
2023-04-12 13:40 ` Peter Zijlstra
2023-05-17 7:41 ` Charlemagne Lasse
2023-04-05 14:17 ` [PATCH v2 4/5] locking/x86: Define arch_try_cmpxchg_local Uros Bizjak
2023-04-05 14:17 ` Uros Bizjak [this message]
2023-04-05 16:37 ` [PATCH v2 0/5] locking: Introduce local{,64}_try_cmpxchg Dave Hansen
2023-04-05 18:53 ` Uros Bizjak
2023-04-06 8:25 ` David Laight
2023-04-06 8:38 ` Uros Bizjak
2023-04-06 9:01 ` David Laight
2023-04-11 11:35 ` Mark Rutland
2023-04-11 13:43 ` Dave Hansen
2023-04-11 21:34 ` David Laight
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