* KAMEZAWA Hiroyuki <[EMAIL PROTECTED]> [2008-12-11 10:05:01]:
> On Wed, 10 Dec 2008 16:52:57 -0800
> Paul Menage <[EMAIL PROTECTED]> wrote:
>
> > On Wed, Dec 10, 2008 at 4:49 PM, KAMEZAWA Hiroyuki
> > <[EMAIL PROTECTED]> wrote:
> > >
> > > an operation like rmdir() in somewhere.
> > > hierarchy_lock for A (acquired)
> > > hierarchy_lock for B (waiting)
> > >
> > > in subsys A.
> > > mmap_sem (acquired)
> > > hierarchy_lock for A (waiting)
> > > in subsys B.
> > > hierarchy_lock for B (aquired)
> > > mmap_sem (waiting)
> > >
> >
> > That's a valid deadlock - you'd need to require the mmap_sem nests
> > either inside all hierarchy_mutexes or else outside all of them.
> >
> This was a found dead lock between memcg and cpuset.
>
> another one was
>
> an operation like rmdir() in somewhere.
> hierarchy_lock for memcg (acquired)
> hierarchy_lock for B (waiting)
>
> in subsys B.
> hierarchy_lock for B (aquired)
But then the hierarchy_locks acquired will be different right?
> have to do some memory reclaim -> hierarchy_lock for memcg
> (waiting)
>
> I have no objections to hierarchy_lock itself but calling context to memcg is
> very
> complicated and simple replace of these locks will be just a small help.
Could you please explain the race better?
--
Balbir
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