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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.
    > Which kernel it is and what filesystems are there? Is there nfsd anywhere
    > in the mix?

    Linus tree as of rc1, with 5ceb9ce6fe94 reverted, and a bunch of patches to
    shut up noisy printk's that get spewed during fuzz testing.

    No active nfs exports/mounts, though something caused nfsd.ko to get loaded
    at some point (module use count of 13, weird).


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