Based on discussions on the svn-src mailing list, rework r218195:

 - entirely eliminate some calls to uio_yeild() as being unnecessary,
   such as in a sysctl handler.

 - move should_yield() and maybe_yield() to kern_synch.c and move the
   prototypes from sys/uio.h to sys/proc.h

 - add a slightly more generic kern_yield() that can replace the
   functionality of uio_yield().

 - replace source uses of uio_yield() with the functional equivalent,
   or in some cases do not change the thread priority when switching.

 - fix a logic inversion bug in vlrureclaim(), pointed out by bde@.

 - instead of using the per-cpu last switched ticks, use a per thread
   variable for should_yield().  With PREEMPTION, the only reasonable
   use of this is to determine if a lock has been held a long time and
   relinquish it.  Without PREEMPTION, this is essentially the same as
   the per-cpu variable.

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index b81e2f8..5d0fd78 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -2234,7 +2234,7 @@ buf_daemon()
 		while (numdirtybuffers > lodirtybuffers) {
 			if (buf_do_flush(NULL) == 0)
 				break;
-			uio_yield();
+			kern_yield(-1);
 		}
 		lodirtybuffers = lodirtysave;