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From: Namhyung Kim <namhyung@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Jiri Olsa <jolsa@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>, Hao Luo <haoluo@google.com>,
	Song Liu <song@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	bpf@vger.kernel.org, linux-perf-users@vger.kernel.org,
	Ian Rogers <irogers@google.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v3 1/3] perf lock contention: Clear lock addr after use
Date: Thu, 26 Oct 2023 10:11:12 -0700	[thread overview]
Message-ID: <169833996388.1181734.6181786783343850640.b4-ty@kernel.org> (raw)
In-Reply-To: <20231020204741.1869520-1-namhyung@kernel.org>

On Fri, 20 Oct 2023 13:47:39 -0700, Namhyung Kim wrote:
> It checks the current lock to calculated the delta of contention time.
> The address is saved in the tstamp map which is allocated at begining of
> contention and released at end of contention.
> 
> But it's possible for bpf_map_delete_elem() to fail.  In that case, the
> element in the tstamp map kept for the current lock and it makes the
> next contention for the same lock tracked incorrectly.  Specificially
> the next contention begin will see the existing element for the task and
> it'd just return.  Then the next contention end will see the element and
> calculate the time using the timestamp for the previous begin.
> 
> [...]

Applied to perf-tools-next, thanks!

      parent reply	other threads:[~2023-10-26 17:11 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-20 20:47 [PATCH v3 1/3] perf lock contention: Clear lock addr after use Namhyung Kim
2023-10-20 20:47 ` [PATCH v3 2/3] perf lock contention: Check race in tstamp elem creation Namhyung Kim
2023-10-25  4:13   ` Ian Rogers
2023-10-20 20:47 ` [PATCH v3 3/3] perf lock contention: Use per-cpu array map for spinlocks Namhyung Kim
2023-10-25  4:15   ` Ian Rogers
2023-10-25  4:13 ` [PATCH v3 1/3] perf lock contention: Clear lock addr after use Ian Rogers
2023-10-26 17:11 ` Namhyung Kim [this message]

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