linux-kernel - Re: [PATCH v3] perf/core: fix mlock accounting in perf

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Message-ID: <0E502E71-B1A8-493B-BD9F-24F15BEDA1D6@fb.com>
Date:   Fri, 24 Jan 2020 21:28:26 +0000
From:   Song Liu <songliubraving@...com>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
CC:     linux-kernel <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3] perf/core: fix mlock accounting in perf_mmap()

Thanks Alex!

> On Jan 24, 2020, at 1:25 AM, Alexander Shishkin <alexander.shishkin@...ux.intel.com> wrote:
> 
> Song Liu <songliubraving@...com> writes:
> 
>> Eecreasing sysctl_perf_event_mlock between two consecutive perf_mmap()s of
> 
> Typo: "Decreasing".

Peter, could you please fix this typo when you apply the patch? I guess
it is not necessary to spam the list with a v4 just for this typo. 

Thanks,
Song

> 
>> a perf ring buffer may lead to an integer underflow in locked memory
>> accounting. This may lead to the undesired behaviors, such as failures in
>> BPF map creation.
>> 
>> Address this by adjusting the accounting logic to take into account the
>> possibility that the amount of already locked memory may exceed the
>> current limit.
>> 
>> Fixes: c4b75479741c ("perf/core: Make the mlock accounting simple again")
>> Signed-off-by: Song Liu <songliubraving@...com>
>> Suggested-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
>> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
>> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
>> Cc: Jiri Olsa <jolsa@...nel.org>
>> Cc: Peter Zijlstra <peterz@...radead.org>
> 
> Other than that,
> 
> Acked-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> 
> Thanks,
> --
> Alex