linux-kernel - Re: [PATCH 0/4] perf: Make SIGTRAP and __perf_pending

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Date: Mon, 11 Mar 2024 17:31:09 +0100
From: Marco Elver <elver@...gle.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Adrian Hunter <adrian.hunter@...el.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Ian Rogers <irogers@...gle.com>, Ingo Molnar <mingo@...hat.com>, 
	Jiri Olsa <jolsa@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Namhyung Kim <namhyung@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/4] perf: Make SIGTRAP and __perf_pending_irq() work on RT.

On Mon, 11 Mar 2024 at 16:59, Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>
> On 2024-03-11 11:34:18 [+0100], Marco Elver wrote:
> > Unfortunately there's a bug in it somewhere. It can be reproduced with
> > tools/testing/selftests/perf_events/remove_on_exec.
> >
> > (FWIW, the kselftests in that directory are more aggressive test cases
> > that I never figured out how to properly port to the 'perf test'
> > framework: sigtrap_threads is a more aggressive version of the 'sigtrap'
> > perf test, and remove_on_exec has no perf test counterpart.)
>
> You posted to warnings, I can only reproduce the second one. Based on the
> backtrace it is obvious what happens and I dare to say that I know why…
> Let me try address them.

I guess I got lucky with hitting 2 warnings instantly. It might be
necessary to run remove_on_exec several times, or even start several
instances of it concurrently (something like "for x in {0..100}; do
(./remove_on_exec &); done" might do the trick).