From 9e761bff03e137fca0c41fd3bcc3e88167d59dc1 Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Mon, 3 Jul 2023 17:00:59 +0200 Subject: [PATCH] drm/amdgpu: Use local64_try_cmpxchg in amdgpu_perf_read MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Use local64_try_cmpxchg instead of local64_cmpxchg (*ptr, old, new) == old in amdgpu_perf_read. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails. There is no need to re-read the value in the loop. No functional change intended. Cc: Alex Deucher Cc: "Christian König" Cc: "Pan, Xinhui" Cc: David Airlie Cc: Daniel Vetter Signed-off-by: Uros Bizjak Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c index 71ee361d0972..6e91ea1de5aa 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c @@ -276,9 +276,8 @@ static void amdgpu_perf_read(struct perf_event *event) (!pe->adev->df.funcs->pmc_get_count)) return; + prev = local64_read(&hwc->prev_count); do { - prev = local64_read(&hwc->prev_count); - switch (hwc->config_base) { case AMDGPU_PMU_EVENT_CONFIG_TYPE_DF: case AMDGPU_PMU_EVENT_CONFIG_TYPE_XGMI: @@ -289,7 +288,7 @@ static void amdgpu_perf_read(struct perf_event *event) count = 0; break; } - } while (local64_cmpxchg(&hwc->prev_count, prev, count) != prev); + } while (!local64_try_cmpxchg(&hwc->prev_count, &prev, count)); local64_add(count - prev, &event->count); } -- 2.11.0