• Roland Dreier's avatar
    iscsi-target: Fix missed wakeup race in TX thread · d5627acb
    Roland Dreier authored
    
    
    The sleeping code in iscsi_target_tx_thread() is susceptible to the classic
    missed wakeup race:
    
     - TX thread finishes handle_immediate_queue() and handle_response_queue(),
       thinks both queues are empty.
     - Another thread adds a queue entry and does wake_up_process(), which does
       nothing because the TX thread is still awake.
     - TX thread does schedule_timeout() and sleeps forever.
    
    In practice this can kill an iSCSI connection if for example an initiator
    does single-threaded writes and the target misses the wakeup window when
    queueing an R2T; in this case the connection will be stuck until the
    initiator loses patience and does some task management operation (or kills
    the connection entirely).
    
    Fix this by converting to wait_event_interruptible(), which does not
    suffer from this sort of race.
    Signed-off-by: default avatarRoland Dreier <roland@purestorage.com>
    Cc: Andy Grover <agrover@redhat.com>
    Cc: Hannes Reinecke <hare@suse.de>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
    d5627acb