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Yang Jihong 15def34e26 perf/core: Fix hardlockup failure caused by perf throttle

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230227023508.102230-1-yangjihong1@huawei.com

2023-04-14 16:08:22 +02:00

callchain.c

uaccess: remove CONFIG_SET_FS

2022-02-25 09:36:06 +01:00

core.c

perf/core: Fix hardlockup failure caused by perf throttle

2023-04-14 16:08:22 +02:00

hw_breakpoint_test.c

perf/hw_breakpoint: test: Skip the test if dependencies unmet

2022-11-02 12:22:05 +01:00

hw_breakpoint.c

perf/hw_breakpoint: Annotate tsk->perf_event_mutex vs ctx->mutex