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From: Alexander Motin <mav@FreeBSD.org>
Date: Sun, 19 Sep 2010 19:52:26 +0000 (UTC)
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Subject: svn commit: r212876 - stable/7/sys/geom
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Author: mav
Date: Sun Sep 19 19:52:26 2010
New Revision: 212876
URL: http://svn.freebsd.org/changeset/base/212876

Log:
  MFC r201264:
  Call wakeup() only for the first request on the queue.

Modified:
  stable/7/sys/geom/geom_io.c
Directory Properties:
  stable/7/sys/   (props changed)
  stable/7/sys/cddl/contrib/opensolaris/   (props changed)
  stable/7/sys/contrib/dev/acpica/   (props changed)
  stable/7/sys/contrib/pf/   (props changed)

Modified: stable/7/sys/geom/geom_io.c
==============================================================================
--- stable/7/sys/geom/geom_io.c	Sun Sep 19 19:51:14 2010	(r212875)
+++ stable/7/sys/geom/geom_io.c	Sun Sep 19 19:52:26 2010	(r212876)
@@ -322,6 +322,7 @@ void
 g_io_request(struct bio *bp, struct g_consumer *cp)
 {
 	struct g_provider *pp;
+	int first;
 
 	KASSERT(cp != NULL, ("NULL cp in g_io_request"));
 	KASSERT(bp != NULL, ("NULL bp in g_io_request"));
@@ -388,12 +389,14 @@ g_io_request(struct bio *bp, struct g_co
 
 	pp->nstart++;
 	cp->nstart++;
+	first = TAILQ_EMPTY(&g_bio_run_down.bio_queue);
 	TAILQ_INSERT_TAIL(&g_bio_run_down.bio_queue, bp, bio_queue);
 	g_bio_run_down.bio_queue_length++;
 	g_bioq_unlock(&g_bio_run_down);
 
 	/* Pass it on down. */
-	wakeup(&g_wait_down);
+	if (first)
+		wakeup(&g_wait_down);
 }
 
 void
@@ -401,6 +404,7 @@ g_io_deliver(struct bio *bp, int error)
 {
 	struct g_consumer *cp;
 	struct g_provider *pp;
+	int first;
 
 	KASSERT(bp != NULL, ("NULL bp in g_io_deliver"));
 	pp = bp->bio_to;
@@ -454,11 +458,13 @@ g_io_deliver(struct bio *bp, int error)
 	pp->nend++;
 	if (error != ENOMEM) {
 		bp->bio_error = error;
+		first = TAILQ_EMPTY(&g_bio_run_up.bio_queue);
 		TAILQ_INSERT_TAIL(&g_bio_run_up.bio_queue, bp, bio_queue);
 		bp->bio_flags |= BIO_ONQUEUE;
 		g_bio_run_up.bio_queue_length++;
 		g_bioq_unlock(&g_bio_run_up);
-		wakeup(&g_wait_up);
+		if (first)
+			wakeup(&g_wait_up);
 		return;
 	}
 	g_bioq_unlock(&g_bio_run_up);