linux-kernel - Re: [PATCH 03/10] perf sched timehist: Handle zero sample->tid properly

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Date:   Tue, 6 Dec 2016 12:59:27 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     David Ahern <dsahern@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <andi@...stfloor.org>,
        Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH 03/10] perf sched timehist: Handle zero sample->tid properly

Hi David,

On Tue, Dec 6, 2016 at 12:52 PM, David Ahern <dsahern@...il.com> wrote:
> On 12/5/16 7:40 PM, Namhyung Kim wrote:
>> Sometimes samples have tid of 0 but non-0 pid.  It ends up having a
>
> Any idea how that happens?

No, I didn't investigate it yet.  Looking at the original code, you
seemed to have same issue and workaround like checking prev_pid or
callchains, right?

Thanks,
Namhyung

>
>> new thread of 0 tid/pid (instead of referring idle task) since tid is
>> used to search matching task.  But I guess it's wrong to use 0 as a
>> tid when pid is set.  This patch uses tid only if it has a non-zero
>> value or same as pid (of 0).