[PATCH V2 0/2] ftrace: Introduce the new I/F "nr_saved_cmdlines"

[Yoshihiro YUNOMAE]

Hi,

This patch set introduces the new I/F "nr_saved_cmdlines" for increasing
the number of saved cmdlines. Current saved_cmdlines can store just 128 command 
names and PIDs, but process names are often lost like <...> when we read trace
data. If the process exists, we can get the name by using ps command. However,
if the process already has not existed, we cannot get the name.

To solve this issue, we introduce the new I/F "nr_saved_cmdlines" to expand
the max number of saved command line names. This I/F is very simple.
If we write a number to nr_saved_cmdlines, the number of command name will be
stored. And, if we read the I/F, we can get current maximum number of command
name. The default number is 128 which is current default number, so this patch
does not change the usage of memory for saved_cmdlines when we boot kernel.

Thanks!

Changes in V2:
- Fix a racing problem of savedcmd between saved_cmdlines I/F and
  nr_saved_cmdlines I/F. If one reads saved_cmdlines and writes a value to
  nr_saved_cmdlines at the same time, then the write returns -EBUSY. [2/2]

---

Yoshihiro YUNOMAE (2):
      ftrace: Make saved_cmdlines use seq_read
      ftrace: Introduce nr_saved_cmdlines I/F


 kernel/trace/trace.c |  316 +++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 261 insertions(+), 55 deletions(-)

-- 
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@xxxxxxxxxxx
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