Hi,
By reading the code of kernel 2.6, I don't understand what's the
exact difference between blk_run_queue() and generic_unplug_device().
Here is the code of generic_unplug_device() :
1279 void generic_unplug_device(request_queue_t *q)
1280 {
1281 spin_lock_irq(q->queue_lock);
1282 __generic_unplug_device(q);
1283 spin_unlock_irq(q->queue_lock);
1284 }
What it does is:
1252 void __generic_unplug_device(request_queue_t *q)
1253 {
1254 if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
1255 return;
1256
1257 if (!blk_remove_plug(q))
1258 return;
1259
1260 /*
1261 * was plugged, fire request_fn if queue has stuff to do
1262 */
1263 if (elv_next_request(q))
1264 q->request_fn(q);
Which seems quite similar to the code of blk_run_queue():
1387 void blk_run_queue(struct request_queue *q)
1388 {
1389 unsigned long flags;
1390
1391 spin_lock_irqsave(q->queue_lock, flags);
1392 blk_remove_plug(q);
1393 q->request_fn(q);
1394 spin_unlock_irqrestore(q->queue_lock, flags);
1395 }
What's the difference between them ? Which one should be used in which
case ?
I have a block driver that issues some requests using submit_bio(). For
most of the request, I let the kernel decides when to unplug the queue,
but for some requests that need to be processed immediatly, I ask the
kernel to forcefully unplug the queue. In 2.4, I used
generic_unplug_device(), but with the introduction of blk_run_queue()
in 2.6, I don't know which one should be used.
Thanks,
Thomas
--
Thomas Petazzoni - thomas.petazzoni@xxxxxxxx
http://{thomas,sos,kos}.enix.org - http://www.toulibre.org
http://www.{livret,agenda}dulibre.org
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