linux-kernel - Re: [PATCH] perf: Ignore sigtrap for tracepoints destined for other tasks

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Date:   Wed, 17 Nov 2021 15:07:07 +0100
From:   Marco Elver <elver@...gle.com>
To:     peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        namhyung@...nel.org, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com
Cc:     syzbot <syzbot+23843634c323e144fd0b@...kaller.appspotmail.com>,
        andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
        daniel@...earbox.net, john.fastabend@...il.com, kafai@...com,
        kpsingh@...nel.org, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, netdev@...r.kernel.org,
        songliubraving@...com, syzkaller-bugs@...glegroups.com, yhs@...com
Subject: Re: [PATCH] perf: Ignore sigtrap for tracepoints destined for other tasks

On Tue, 9 Nov 2021 at 13:22, Marco Elver <elver@...gle.com> wrote:
> syzbot reported that the warning in perf_sigtrap() fires, saying that
> the event's task does not match current:
>
>  | WARNING: CPU: 0 PID: 9090 at kernel/events/core.c:6446 perf_pending_event+0x40d/0x4b0 kernel/events/core.c:6513
[...]
> This happened because the 'sched_wakeup' tracepoint also takes a task
> argument passed on to perf_tp_event(), which is used to deliver the
> event to that other task.
>
> Since we cannot deliver synchronous signals to other tasks, skip an event if
> perf_tp_event() is targeted at another task and perf_event_attr::sigtrap is
> set, which will avoid ever entering perf_sigtrap() for such events.
[...]

Hmm, I made the mistake of sending this in the merge-window.
Any comments?

Thanks,
-- Marco