linux-kernel - Re: [PATCH v2] perf/core: install cgroup events to correct cpuctx

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Date:   Fri, 24 Jan 2020 10:15:52 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Song Liu <songliubraving@...com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        Andi Kleen <andi@...stfloor.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2] perf/core: install cgroup events to correct cpuctx

On Wed, Jan 22, 2020 at 11:50:27AM -0800, Song Liu wrote:
> cgroup events are always installed in the cpuctx. However, when it is not
> installed via IPI, list_update_cgroup_event() adds it to cpuctx of current
> CPU, which triggers the following with CONFIG_DEBUG_LIST:
> 

> [   31.777570] list_add double add: new=ffff888ff7cf0db0, prev=ffff888ff7ce82f0, next=ffff888ff7cf0db0.

> To reproduce this, we can simply run:
>   perf stat -e cs -a &
>   perf stat -e cs -G anycgroup
> 
> Fix this by installing it to cpuctx that contains event->ctx, and the
> proper cgrp_cpuctx_list.
> 
> Fixes: db0503e4f675 ("perf/core: Optimize perf_install_in_event()")
> Suggested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Andi Kleen <andi@...stfloor.org>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Song Liu <songliubraving@...com>

Thanks!