• Jeff Layton's avatar
    locks: wake any locks blocked on request before deadlock check · 7bcb0024
    Jeff Layton authored
    commit 945ab8f6 upstream.
    
    Andreas reported that he was seeing the tdbtorture test fail in some
    cases with -EDEADLCK when it wasn't before. Some debugging showed that
    deadlock detection was sometimes discovering the caller's lock request
    itself in a dependency chain.
    
    While we remove the request from the blocked_lock_hash prior to
    reattempting to acquire it, any locks that are blocked on that request
    will still be present in the hash and will still have their fl_blocker
    pointer set to the current request.
    
    This causes posix_locks_deadlock to find a deadlock dependency chain
    when it shouldn't, as a lock request cannot block itself.
    
    We are going to end up waking all of those blocked locks anyway when we
    go to reinsert the request back into the blocked_lock_hash, so just do
    it prior to checking for deadlocks. This ensures that any lock blocked
    on the current request will no longer be part of any blocked request
    chain.
    
    URL: https://bugzilla.kernel.org/show_bug.cgi?id=202975
    Fixes: 5946c431 ("fs/locks: allow a lock request to block other requests.")
    Cc: stable@vger.kernel.org
    Reported-by: 's avatarAndreas Schneider <asn@redhat.com>
    Signed-off-by: 's avatarNeil Brown <neilb@suse.com>
    Signed-off-by: 's avatarJeff Layton <jlayton@kernel.org>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    7bcb0024
locks.c 77.4 KB