On 09/11/12 01:38, Tejun Heo wrote: > On Fri, Sep 07, 2012 at 08:57:10AM +0200, Bart Van Assche wrote: >> Also, as far as I can see the functions that can insert a request into >> the queue (blk_insert_cloned_request(), queue_unplugged(), >> blk_execute_rq_nowait()) all check whether the queue is dead before >> inserting a request. That should be sufficient to prevent that new >> requests are queued after QUEUE_FLAG_DEAD has been set. > > Yes, but does that guarantee that none would call into ->request_fn()? > If so, fine; otherwise, we may need to add another state to prevent > that.
Good question. As far as I can see calling request_queue.request_fn() is fine as long as the caller holds a reference on the queue. If e.g. scsi_request_fn() would get invoked after blk_drain_queue() finished it will return immediately because it was invoked with an empty request queue. So we should be fine as long as all blk_run_queue() callers either hold a reference on the request queue itself or on the sdev that owns the request queue. As far as I can see if patch http://marc.info/?l=linux-scsi&m=134453905402413 gets accepted then all callers in the SCSI core of blk_run_queue() will hold a (direct or indirect) reference on the request_queue before invoking blk_run_queue() or __blk_run_queue(). Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
