Messages in this thread |  | | | Date | Fri, 17 Sep 2004 03:13:38 -0700 | | From | Mike Christie <> | | Subject | Re: [PATCH] modular io schedulers with online switching, #2 |
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Jens Axboe wrote > +void blk_wait_queue_drained(request_queue_t *q) > +{ > + struct request_list *rl = &q->rq; > + DEFINE_WAIT(wait); > + > + set_bit(QUEUE_FLAG_DRAIN, &q->queue_flags); > + > + prepare_to_wait(&rl->drain, &wait, TASK_UNINTERRUPTIBLE); > + do { > + spin_lock_irq(q->queue_lock); > + if (!rl->count[READ] && !rl->count[WRITE]) { > + spin_unlock_irq(q->queue_lock); > + break; > + } > + > + __generic_unplug_device(q); > + spin_unlock_irq(q->queue_lock); > + io_schedule(); > + } while (1); > + finish_wait(&rl->drain, &wait); > +} > +
Jens,
If a driver does not allocate requests through blk_get_request, will the rl->count[] tests need to be changed or do those drivers need to be changed? For example, if SCSI insterts a special request into the queue, then someone swaps the io scheduler with no outstanding normal requests (so the rl->counts will be zero), could the special request still be in the queue since it allocated its request using kmalloc (the request is allocated as part of the scsi command).
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