Messages in this thread | | | Date | Mon, 28 Dec 2009 08:44:26 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] perf_event: mount debugfs automatically |
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* Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> wrote:
> Mount debugfs automatically if it's not mounted, umount it > when programme exit > > Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> > --- > tools/perf/perf.c | 10 +++++++++- > tools/perf/util/debugfs.c | 16 +++++++--------- > tools/perf/util/debugfs.h | 2 +- > 3 files changed, 17 insertions(+), 11 deletions(-)
I'm not sure that's a good idea. What happens if two perf tools are running in parallel:
perf report #1 start perf report #2 start perf report #2 exit [umount debugfs] perf report #2 tries to open /debug file: kaboom perf report #2 exit
But your idea is sound if we only do the first half: we should mount it under /sys/kernel/debug/ if it's not mounted already [and that directory is available], and leave it mounted there.
Furthermore please not that we must not mount it under any other path - mounting is always a dangerous operation because it changes the VFS namespace. For example some system might have some local files under /debug for whatever reason, we must not over-mount it and potentially destroy data because we'd confuse an app that writes into /debug. /sys/kernel/debug/ is a fair game to mount into OTOH.
(and even then we should just leave it mounted and never umount it.)
Thanks,
Ingo
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