diff --git a/[refs] b/[refs]
index 491e694a6a31..9ff586d516b0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2557a933b795c1988c721ebb871cd735128bb9cb
+refs/heads/master: 5b13d863573e746739ccfc24ac1a9473cfee8df1
diff --git a/trunk/arch/x86/kernel/tsc_32.c b/trunk/arch/x86/kernel/tsc_32.c
index d7498b34c8e9..f14cfd9d1f94 100644
--- a/trunk/arch/x86/kernel/tsc_32.c
+++ b/trunk/arch/x86/kernel/tsc_32.c
@@ -287,27 +287,14 @@ core_initcall(cpufreq_tsc);
 /* clock source code */
 
 static unsigned long current_tsc_khz = 0;
-static struct clocksource clocksource_tsc;
 
-/*
- * We compare the TSC to the cycle_last value in the clocksource
- * structure to avoid a nasty time-warp issue. This can be observed in
- * a very small window right after one CPU updated cycle_last under
- * xtime lock and the other CPU reads a TSC value which is smaller
- * than the cycle_last reference value due to a TSC which is slighty
- * behind. This delta is nowhere else observable, but in that case it
- * results in a forward time jump in the range of hours due to the
- * unsigned delta calculation of the time keeping core code, which is
- * necessary to support wrapping clocksources like pm timer.
- */
 static cycle_t read_tsc(void)
 {
 	cycle_t ret;
 
 	rdtscll(ret);
 
-	return ret >= clocksource_tsc.cycle_last ?
-		ret : clocksource_tsc.cycle_last;
+	return ret;
 }
 
 static struct clocksource clocksource_tsc = {
diff --git a/trunk/arch/x86/kernel/tsc_64.c b/trunk/arch/x86/kernel/tsc_64.c
index 01fc9f0c39e2..947554ddabb6 100644
--- a/trunk/arch/x86/kernel/tsc_64.c
+++ b/trunk/arch/x86/kernel/tsc_64.c
@@ -11,7 +11,6 @@
 #include <asm/hpet.h>
 #include <asm/timex.h>
 #include <asm/timer.h>
-#include <asm/vgtod.h>
 
 static int notsc __initdata = 0;
 
@@ -291,34 +290,18 @@ int __init notsc_setup(char *s)
 
 __setup("notsc", notsc_setup);
 
-static struct clocksource clocksource_tsc;
 
-/*
- * We compare the TSC to the cycle_last value in the clocksource
- * structure to avoid a nasty time-warp. This can be observed in a
- * very small window right after one CPU updated cycle_last under
- * xtime/vsyscall_gtod lock and the other CPU reads a TSC value which
- * is smaller than the cycle_last reference value due to a TSC which
- * is slighty behind. This delta is nowhere else observable, but in
- * that case it results in a forward time jump in the range of hours
- * due to the unsigned delta calculation of the time keeping core
- * code, which is necessary to support wrapping clocksources like pm
- * timer.
- */
+/* clock source code: */
 static cycle_t read_tsc(void)
 {
 	cycle_t ret = (cycle_t)get_cycles();
-
-	return ret >= clocksource_tsc.cycle_last ?
-		ret : clocksource_tsc.cycle_last;
+	return ret;
 }
 
 static cycle_t __vsyscall_fn vread_tsc(void)
 {
 	cycle_t ret = (cycle_t)vget_cycles();
-
-	return ret >= __vsyscall_gtod_data.clock.cycle_last ?
-		ret : __vsyscall_gtod_data.clock.cycle_last;
+	return ret;
 }
 
 static struct clocksource clocksource_tsc = {
diff --git a/trunk/drivers/virtio/virtio_ring.c b/trunk/drivers/virtio/virtio_ring.c
index c2fa5c630813..aa714028641e 100644
--- a/trunk/drivers/virtio/virtio_ring.c
+++ b/trunk/drivers/virtio/virtio_ring.c
@@ -214,7 +214,10 @@ static void vring_disable_cb(struct virtqueue *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
+	START_USE(vq);
+	BUG_ON(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);
 	vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
+	END_USE(vq);
 }
 
 static bool vring_enable_cb(struct virtqueue *_vq)
diff --git a/trunk/include/linux/virtio.h b/trunk/include/linux/virtio.h
index e7d10845b3c1..12c18ac1b973 100644
--- a/trunk/include/linux/virtio.h
+++ b/trunk/include/linux/virtio.h
@@ -41,8 +41,6 @@ struct virtqueue
  *	Returns NULL or the "data" token handed to add_buf.
  * @disable_cb: disable callbacks
  *	vq: the struct virtqueue we're talking about.
- *	Note that this is not necessarily synchronous, hence unreliable and only
- *	useful as an optimization.
  * @enable_cb: restart callbacks after disable_cb.
  *	vq: the struct virtqueue we're talking about.
  *	This re-enables callbacks; it returns "false" if there are pending
@@ -50,8 +48,7 @@ struct virtqueue
  *	checking for more work, and enabling callbacks.
  *
  * Locking rules are straightforward: the driver is responsible for
- * locking.  No two operations may be invoked simultaneously, with the exception
- * of @disable_cb.
+ * locking.  No two operations may be invoked simultaneously.
  *
  * All operations can be called in any context.
  */