linux-kernel - Question on perf event context swap at process switch

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Date:   Fri, 22 Jul 2022 20:17:25 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Jiri Olsa <olsajiri@...il.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Question on perf event context swap at process switch

Hi Peter,

Consider two processes having clone contexts (for example, two children of
the same parent). While process switch between these two, the perf event
context would get swapped but event->hw.target will point to other sibling's
task_struct. If that process exit just after one context swap, _free_event()
will call put_task_context() on sibling process' task_struct. Wouldn't it
result into fatal error later?

Thanks,
Ravi