linux-kernel - Re: [PATCH -mm 4/5] tools/perf: replace hard-coded 16 with TASK_COMM

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Date:   Thu, 9 Dec 2021 10:42:15 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Petr Mladek <pmladek@...e.com>,
        David Hildenbrand <david@...hat.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Linux MM <linux-mm@...ck.org>, bpf <bpf@...r.kernel.org>,
        "linux-perf-use." <linux-perf-users@...r.kernel.org>,
        Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Michal Miroslaw <mirq-linux@...e.qmqm.pl>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH -mm 4/5] tools/perf: replace hard-coded 16 with TASK_COMM_LEN

On Thu, Dec 9, 2021 at 2:43 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Sat,  4 Dec 2021 09:52:55 +0000
> Yafang Shao <laoar.shao@...il.com> wrote:
>
> > @@ -43,7 +45,7 @@ static int test__perf_evsel__tp_sched_test(struct test_suite *test __maybe_unuse
> >               return -1;
> >       }
> >
> > -     if (evsel__test_field(evsel, "prev_comm", 16, false))
> > +     if (evsel__test_field(evsel, "prev_comm", TASK_COMM_LEN, false))
> >               ret = -1;
> >
> >       if (evsel__test_field(evsel, "prev_pid", 4, true))
> > @@ -55,7 +57,7 @@ static int test__perf_evsel__tp_sched_test(struct test_suite *test __maybe_unuse
> >       if (evsel__test_field(evsel, "prev_state", sizeof(long), true))
> >               ret = -1;
> >
> > -     if (evsel__test_field(evsel, "next_comm", 16, false))
> > +     if (evsel__test_field(evsel, "next_comm", TASK_COMM_LEN, false))
> >               ret = -1;
> >
> >       if (evsel__test_field(evsel, "next_pid", 4, true))
> > @@ -73,7 +75,7 @@ static int test__perf_evsel__tp_sched_test(struct test_suite *test __maybe_unuse
> >               return -1;
> >       }
> >
> > -     if (evsel__test_field(evsel, "comm", 16, false))
> > +     if (evsel__test_field(evsel, "comm", TASK_COMM_LEN, false))
>
> Shouldn't all these be TASK_COMM_LEN_16?
>

The value here must be the same with TASK_COMM_LEN, so I use TASK_COMM_LEN here.
But we may also change the code as
https://lore.kernel.org/lkml/20211101060419.4682-9-laoar.shao@gmail.com/
if TASK_COMM_LEN is changed, so TASK_COMM_LEN_16 is also okay here.
I will change it to TASK_COMM_LEN_16 in the next version.

>
> >               ret = -1;
> >
> >       if (evsel__test_field(evsel, "pid", 4, true))
>


-- 
Thanks
Yafang