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Date: Wed, 13 Mar 2024 15:15:50 +0100
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	Adrian Hunter <adrian.hunter@intel.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Ian Rogers <irogers@google.com>, Ingo Molnar <mingo@redhat.com>,
	Jiri Olsa <jolsa@kernel.org>, Marco Elver <elver@google.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v2 0/4] perf: Make SIGTRAP and __perf_pending_irq() work
 on RT.
Message-ID: <20240313141550.eG5aJcAq@linutronix.de>
References: <ZfGqCWzyVzyGQrAQ@x1>
 <ZfGudRl9-tB_TszO@x1>
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In-Reply-To: <ZfGudRl9-tB_TszO@x1>

On 2024-03-13 10:47:33 [-0300], Arnaldo Carvalho de Melo wrote:
> /* For exec'd child. */
> static void exec_child(void)
> {
>         struct sigaction action =3D {};
>         const int val =3D 42;
>=20
>         /* Set up sigtrap handler in case we erroneously receive a trap. =
*/
>         action.sa_flags =3D SA_SIGINFO | SA_NODEFER;
>         action.sa_sigaction =3D sigtrap_handler;
>         sigemptyset(&action.sa_mask);
>         if (sigaction(SIGTRAP, &action, NULL))
>                 _exit((perror("sigaction failed"), 1));
>=20
>         /* Signal parent that we're starting to spin. */
>         if (write(STDOUT_FILENO, &val, sizeof(int)) =3D=3D -1)
>                 _exit((perror("write failed"), 1));
>=20
>         /* Should hang here until killed. */
>         while (!signal_count);
> }
>=20
> So probably just a test needing to be a bit more polished?

Maybe. I'm not sure where this is coming from. Either someone should
kill or the signal should be delivered but, hmm=E2=80=A6 If the signal isn't
coming then it might one of those without a perf counter.

> Seems like it, on a newer machine, faster, I managed to reproduce it on
> a non-RT kernel, with one exec_child remaining:

Okay, so no regression. That is something ;)

> - Arnaldo

Sebastian