linux-kernel - Re: [PATCH] tools lib traceevent: Fix prev/next

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Date:   Tue, 3 Jan 2017 10:00:59 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] tools lib traceevent: Fix prev/next_prio for deadline
 tasks

On Tue,  3 Jan 2017 12:42:42 +0100
Daniel Bristot de Oliveira <bristot@...hat.com> wrote:

> From: Daniel Bristot de Oliveiva <bristot@...hat.com>
> 
> Currently, the sched:sched_switch tracepoint reports deadline tasks
> with priority -1. But when reading the trace via perf script I've
> got the following output:
> 
>   # ./d & # (d is a deadline task, see [1])
>   # perf record -e sched:sched_switch -a sleep 1
>   # perf script
>       ...
>          swapper     0 [000]  2146.962441: sched:sched_switch: swapper/0:0 [120] R ==> d:2593 [4294967295]
>                d  2593 [000]  2146.972472: sched:sched_switch: d:2593 [4294967295] R ==> g:2590 [4294967295]
> 
> The task d reports the wrong priority [4294967295]. This happens because
> the "int prio" is stored in an unsigned long long val. Although it is
> set as a %lld, as int is shorter than unsigned long long,
> trace_seq_printf prints it as a positive number.
> 
> The fix is just to cast the val as an int, and print it as a %d,
> as in the sched:sched_switch tracepoint's "format".
> 
> The output with the fix is:
> 
>   # ./d &
>   # perf record -e sched:sched_switch -a sleep 1
>   # perf script
>       ...
>          swapper     0 [000]  4306.374037: sched:sched_switch: swapper/0:0 [120] R ==> d:10941 [-1]
>                d 10941 [000]  4306.383823: sched:sched_switch: d:10941 [-1] R ==> swapper/0:0 [120]
> 
> [1] gcc -o d d.c - from http://bristot.me/lkml/d.c
> 
> Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: linux-kernel@...r.kernel.org
> 
Acked-by: Steven Rostedt <rostedt@...dmis.org>

---
:-)

-- Steve