From dffaf91aa34835df0cee971de3c3bc7003398112 Mon Sep 17 00:00:00 2001
From: Tor Egge <tegge@FreeBSD.org>
Date: Mon, 16 Jan 2006 22:09:47 +0000
Subject: [PATCH] Set flag in needsbuffer while still holding bqlock to avoid
 lost wakeup.

---
 sys/kern/vfs_bio.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index c5192596a98..aa393aff2c4 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -1907,7 +1907,6 @@ restart:
 		int flags;
 		char *waitmsg;
 
-		mtx_unlock(&bqlock);
 		if (defrag) {
 			flags = VFS_BIO_NEED_BUFSPACE;
 			waitmsg = "nbufkv";
@@ -1918,11 +1917,14 @@ restart:
 			waitmsg = "newbuf";
 			flags = VFS_BIO_NEED_ANY;
 		}
+		mtx_lock(&nblock);
+		needsbuffer |= flags;
+		mtx_unlock(&nblock);
+		mtx_unlock(&bqlock);
 
 		bd_speedup();	/* heeeelp */
 
 		mtx_lock(&nblock);
-		needsbuffer |= flags;
 		while (needsbuffer & flags) {
 			if (msleep(&needsbuffer, &nblock,
 			    (PRIBIO + 4) | slpflag, waitmsg, slptimeo)) {