Messages in this thread Patch in this message | | | From | Yang Jihong <> | Subject | [PATCH RESEND v3] perf/core: Fix hardlockup failure caused by perf throttle | Date | Mon, 27 Feb 2023 10:35:08 +0800 |
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commit e050e3f0a71bf ("perf: Fix broken interrupt rate throttling") introduces a change in throttling threshold judgment. Before this, compare hwc->interrupts and max_samples_per_tick, then increase hwc->interrupts by 1, but this commit reverses order of these two behaviors, causing the semantics of max_samples_per_tick to change. In literal sense of "max_samples_per_tick", if hwc->interrupts == max_samples_per_tick, it should not be throttled, therefore, the judgment condition should be changed to "hwc->interrupts > max_samples_per_tick".
In fact, this may cause the hardlockup to fail, The minimum value of max_samples_per_tick may be 1, in this case, the return value of __perf_event_account_interrupt function is 1. As a result, nmi_watchdog gets throttled, which would stop PMU (Use x86 architecture as an example, see x86_pmu_handle_irq).
Fixes: e050e3f0a71b ("perf: Fix broken interrupt rate throttling") Signed-off-by: Yang Jihong <yangjihong1@huawei.com> ---
Changes since v2: - Add fixed commit.
Changes since v1: - Modify commit title.
kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c index f79fd8b87f75..0540a8653906 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9434,7 +9434,7 @@ __perf_event_account_interrupt(struct perf_event *event, int throttle) } else { hwc->interrupts++; if (unlikely(throttle - && hwc->interrupts >= max_samples_per_tick)) { + && hwc->interrupts > max_samples_per_tick)) { __this_cpu_inc(perf_throttled_count); tick_dep_set_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS); hwc->interrupts = MAX_INTERRUPTS; -- 2.30.GIT
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