Messages in this thread Patch in this message |  | | Date | Wed, 29 Nov 2000 19:11:57 +0100 | From | Jens Axboe <> | Subject | Re: plug problem in linux-2.4.0-test11 |
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On Wed, Nov 29 2000, Linus Torvalds wrote: > I would much rather actually go back to the original setup, which did > nothing at all if the queue wasn't plugged in the first place.
But that potentially breaks devices that either don't use plugging or alternatively implement their own, because q->plugged will not get set and the unplug from __get_request_wait does nothing. It's clear that the plug/noplug is too coarse. Anyway, I don't think there's currently a problem with the old setup for any in-kernel drivers so I'm fine with reverting to that behaviour for now.
> I think that we should strive for a setup that calls "request_fn" only to > start new IO, and that expects the low-level driver to be able to do the > whole request queue until it is empty. Then we re-start it the next time > around.
Yes agreed.
--- drivers/block/ll_rw_blk.c~ Wed Nov 29 15:17:33 2000 +++ drivers/block/ll_rw_blk.c Wed Nov 29 19:04:50 2000 @@ -347,9 +347,10 @@ */ static inline void __generic_unplug_device(request_queue_t *q) { - if (!list_empty(&q->queue_head)) { + if (q->plugged) { q->plugged = 0; - q->request_fn(q); + if (!list_empty(&q->queue_head)) + q->request_fn(q); } } -- * Jens Axboe <axboe@suse.de> * SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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