linux-kernel - Re: [PATCH 3/5] kernel/watchdog_hld: Ensure CPU-bound context when creating hardlockup detector event

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Date:   Fri, 25 Feb 2022 14:15:48 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Lecopzer Chen <lecopzer.chen@...iatek.com>
Cc:     linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>, davem@...emloft.net,
        Matthias Brugger <matthias.bgg@...il.com>,
        Marc Zyngier <maz@...nel.org>,
        Julien Thierry <jthierry@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wang Qing <wangqing@...o.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Xiaoming Ni <nixiaoming@...wei.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, sumit.garg@...aro.org,
        kernelfans@...il.com, yj.chiang@...iatek.com
Subject: Re: [PATCH 3/5] kernel/watchdog_hld: Ensure CPU-bound context when
 creating hardlockup detector event

On Sat 2022-02-12 18:43:47, Lecopzer Chen wrote:
> From: Pingfan Liu <kernelfans@...il.com>
> 
> from: Pingfan Liu <kernelfans@...il.com>
> 
> hardlockup_detector_event_create() should create perf_event on the
> current CPU. Preemption could not get disabled because
> perf_event_create_kernel_counter() allocates memory. Instead,
> the CPU locality is achieved by processing the code in a per-CPU
> bound kthread.
> 
> Add a check to prevent mistakes when calling the code in another
> code path.
> 
> Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> Co-developed-by: Lecopzer Chen <lecopzer.chen@...iatek.com>
> Signed-off-by: Lecopzer Chen <lecopzer.chen@...iatek.com>

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr