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| author | Uros Bizjak <ubizjak@gmail.com> | 2024-04-25 12:16:14 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2024-05-18 11:15:13 +0200 |
| commit | cd84351c8c1baec86342d784feb884ace007d51c (patch) | |
| tree | 8ccd6c21b7cd6cc44cf710e2379fb37ccaac474f /arch/x86/events/amd | |
| parent | perf/x86/cstate: Remove unused 'struct perf_cstate_msr' (diff) | |
| download | linux-cd84351c8c1baec86342d784feb884ace007d51c.tar.xz linux-cd84351c8c1baec86342d784feb884ace007d51c.zip | |
perf/x86/amd: Use try_cmpxchg() in events/amd/{un,}core.c
Replace this pattern in events/amd/{un,}core.c:
cmpxchg(*ptr, old, new) == old
... with the simpler and faster:
try_cmpxchg(*ptr, &old, new)
The x86 CMPXCHG instruction returns success in the ZF flag, so this change
saves a compare after the CMPXCHG.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240425101708.5025-1-ubizjak@gmail.com
Diffstat (limited to 'arch/x86/events/amd')
| -rw-r--r-- | arch/x86/events/amd/core.c | 4 | ||||
| -rw-r--r-- | arch/x86/events/amd/uncore.c | 8 |
2 files changed, 9 insertions, 3 deletions
diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c index 1fc4ce44e743..18bfe3451f3a 100644 --- a/arch/x86/events/amd/core.c +++ b/arch/x86/events/amd/core.c @@ -433,7 +433,9 @@ static void __amd_put_nb_event_constraints(struct cpu_hw_events *cpuc, * when we come here */ for (i = 0; i < x86_pmu.num_counters; i++) { - if (cmpxchg(nb->owners + i, event, NULL) == event) + struct perf_event *tmp = event; + + if (try_cmpxchg(nb->owners + i, &tmp, NULL)) break; } } diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c index 4ccb8fa483e6..0fafe233bba4 100644 --- a/arch/x86/events/amd/uncore.c +++ b/arch/x86/events/amd/uncore.c @@ -162,7 +162,9 @@ static int amd_uncore_add(struct perf_event *event, int flags) /* if not, take the first available counter */ hwc->idx = -1; for (i = 0; i < pmu->num_counters; i++) { - if (cmpxchg(&ctx->events[i], NULL, event) == NULL) { + struct perf_event *tmp = NULL; + + if (try_cmpxchg(&ctx->events[i], &tmp, event)) { hwc->idx = i; break; } @@ -196,7 +198,9 @@ static void amd_uncore_del(struct perf_event *event, int flags) event->pmu->stop(event, PERF_EF_UPDATE); for (i = 0; i < pmu->num_counters; i++) { - if (cmpxchg(&ctx->events[i], event, NULL) == event) + struct perf_event *tmp = event; + + if (try_cmpxchg(&ctx->events[i], &tmp, NULL)) break; } |