Re: [PATCH 1/2] tracing/perf: Clear stop state in perf_trace_add()

[sashiko-bot@kernel.org]

> Since commit 18dbcbfabfff ("perf: Fix the POLL_HUP delivery breakage"),
> __perf_event_overflow() stops the event with pmu->stop() and disables
> it when the PERF_EVENT_IOC_REFRESH limit is reached. When userspace
> re-arms the event with PERF_EVENT_IOC_REFRESH, the event is enabled
> again and pmu->add() is called with PERF_EF_START.
> 
> perf_trace_add() sets PERF_HES_STOPPED when PERF_EF_START is missing,
> but never clears it. The flag set by pmu->stop() stays, and
> perf_tp_event_match() drops every later hit. A tracepoint, kprobe or
> uprobe event re-armed this way delivers only its first overflow. This
> breaks self-profilers such as async-profiler, and the "Event re-armed
> with PERF_EVENT_IOC_REFRESH" perf test fails:
> 
>   1000 events, count 1, 1 overflows (1 POLL_HUP), re-arm errno 0
>   Tracepoint event : FAILED!
> 
> Set the state from PERF_EF_START on every add, as perf_swevent_add()
> does.
> 
> Fixes: 18dbcbfabfff ("perf: Fix the POLL_HUP delivery breakage")
> Reported-by: Francesco Nigro <nigro.fra@gmail.com>
> Closes: https://lore.kernel.org/r/20261021131006.2101248-1-nigro.fra@gmail.com/
> Assisted-by: LLM
> Signed-off-by: Paolo Bertinetti <paolobertinetti200f4@proton.me>

Sashiko has reviewed this patch and found no issues.

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