Hi Yoshihiro,
On Thu, 13 Feb 2014 10:28:58 +0900, Yoshihiro YUNOMAE wrote:
> Introduce nr_saved_cmdlines I/F for changing the number of pid-comm list.
> saved_cmdlines can store 128 command names using SAVED_CMDLINES now, but
> 'no-existing processes' names are often lost in saved_cmdlines when we
> read trace data. So, by introducing nr_saved_cmdlines I/F, the rule storing
> 128 command names is changed to the command numbers defined users.
>
> When we write a value to nr_saved_cmdlines, the number of the value will
> be stored in pid-comm list:
>
> # echo 1024 > /sys/kernel/debug/tracing/nr_saved_cmdlines
>
> Here, 1024 command names are stored. The default number is 128 and the maximum
> number is PID_MAX_DEFAULT (=32768 if CONFIG_BASE_SMALL is not set). So, if we
> want to avoid to lose command names, we need to set 32768 to
> nr_saved_cmdlines.
>
> We can read the maximum number of the list:
>
> # cat /sys/kernel/debug/tracing/nr_saved_cmdlines
> 128
[SNIP]
> @@ -3685,7 +3760,8 @@ static void *saved_cmdlines_next(struct seq_file *m,
> void *v, loff_t *pos)
>
> (*pos)++;
>
> - for (; ptr < &map_cmdline_to_pid[SAVED_CMDLINES]; ptr++) {
> + for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
> + ptr++) {
> if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
> continue;
>
> @@ -3700,7 +3776,7 @@ static void *saved_cmdlines_start(struct seq_file *m,
> loff_t *pos)
> void *v;
> loff_t l = 0;
>
> - v = &map_cmdline_to_pid[0];
> + v = &savedcmd->map_cmdline_to_pid[0];
> while (l <= *pos) {
> v = saved_cmdlines_next(m, v, &l);
> if (!v)
Are you accessing the savecmd without trace_cmdline_lock?
Thanks,
Namhyung
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