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SubjectRe: processes hung after sys_renameat, and 'missing' processes
On Mon, Jun 04, 2012 at 12:28:20AM +0100, Al Viro wrote:
> On Mon, Jun 04, 2012 at 12:17:09AM +0100, Al Viro wrote:
> >
> > > Also, sysrq-w is usually way more interesting than 't' when there are
> > > processes stuck on a mutex.
> > >
> > > Because yes, it looks like you have a boattload of trinity processes
> > > stuck on an inode mutex. Looks like every single one of them is in
> > > 'lock_rename()'. It *shouldn't* be an ABBA deadlock, since lockdep
> > > should have noticed that, but who knows.
> >
> > lock_rename() is a bit of a red herring here - they appear to be all
> > within-directory renames, so it's just a "trying to rename something
> > in a directory that has ->i_mutex held by something else".
> >
> > IOW, something else in there is holding ->i_mutex - something that
> > either hadn't been through lock_rename() at all or has already
> > passed through it and still hadn't got around to unlock_rename().
> > In either case, suspects won't have lock_rename() in the trace...
>
> Everything in lock_rename() appears to be at lock_rename+0x3e. Unless
> there's a really huge amount of filesystems on that box, this has to
> be
> mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
> and everything on that sucker is not holding any locks yet. IOW, that's
> the tail hanging off whatever deadlock is there.
>
> One possibility is that something has left the kernel without releasing
> i_mutex on some directory, which would make atomic_open patches the most
> obvious suspects.

Just hit this again on a different box, though this time the stack traces
of the stuck processes seems to vary between fchmod/fchown/getdents calls.

partial dmesg at http://fpaste.org/jBVM/
sysrq-w: http://fpaste.org/uYtj/
sysrq-d: http://fpaste.org/Xxur/

does this give any new clues that the previous traces didn't ?

Dave



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