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SubjectRe: BUG: cgroup_task_counter subsys may crash with whole-threadgroup move
08:09, Ben Blum wrote:
> I was testing some patches for cgroup_attach_proc and managed to cause a
> crash with the following usage pattern:
>
> mount -t cgroup none -o tasks /dev/cgroup
> cd /dev/cgroup
> mkdir foo
> echo $PID > foo/cgroup.procs
> echo $PID > tasks
> echo $PID > foo/cgroup.procs
>
> Where $PID is the thread ID of a member of a multithreaded process (my
> test program just does CLONE_THREAD 8 times and then all threads sleep).
> (It doesn't matter if the thread is the group leader or not, but a
> single-threaded process doesn't crash.)
>
> And get the following kernel panic:
> http://maximegalon.andrew.cmu.edu/cgroup-taskstats/panic.txt
>
> It's deterministic, and happens only when the "tasks" subsystem is
> mounted.
>
> I'm using user-mode linux to test, with the following config:
> http://maximegalon.andrew.cmu.edu/cgroup-taskstats/config.txt
>
> and I ran it in GDB to get the following backtrace:
> http://maximegalon.andrew.cmu.edu/cgroup-taskstats/bt.txt
>

I've figured out what's wrong. Patch will be sent out soon.

Thanks for reporting this!

--
Li Zefan


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