Index: mpath.c
===================================================================
RCS file: /cvs/src/sys/scsi/mpath.c,v
retrieving revision 1.37
diff -u -p -r1.37 mpath.c
--- mpath.c	14 Sep 2014 14:17:26 -0000	1.37
+++ mpath.c	24 Sep 2014 23:49:56 -0000
@@ -340,7 +340,7 @@ mpath_done(struct scsi_xfer *mxs)
 void
 mpath_failover(struct mpath_dev *d)
 {
-	if (!scsi_pending_start(&d->d_mtx, &d->d_failover))
+	if (!scsi_pending_start(&d->d_failover))
 		return;
 
 	mpath_failover_start(d);
@@ -389,7 +389,7 @@ mpath_path_status(struct mpath_path *p, 
 
 	if (status == MPATH_S_ACTIVE) {
 		scsi_xsh_add(&p->p_xsh);
-		if (!scsi_pending_finish(&d->d_mtx, &d->d_failover))
+		if (!scsi_pending_finish(&d->d_failover))
 			mpath_failover_start(d);
 	} else
 		mpath_failover_check(d);
Index: scsi_base.c
===================================================================
RCS file: /cvs/src/sys/scsi/scsi_base.c,v
retrieving revision 1.217
diff -u -p -r1.217 scsi_base.c
--- scsi_base.c	20 Sep 2014 16:18:23 -0000	1.217
+++ scsi_base.c	24 Sep 2014 23:49:56 -0000
@@ -45,6 +45,7 @@
 #include <sys/device.h>
 #include <sys/pool.h>
 #include <sys/task.h>
+#include <sys/atomic.h>
 
 #include <scsi/scsi_all.h>
 #include <scsi/scsi_disk.h>
@@ -201,33 +202,20 @@ scsi_plug_detach(void *xp, void *null)
 }
 
 int
-scsi_pending_start(struct mutex *mtx, u_int *running)
+scsi_pending_start(u_int *running)
 {
-	int rv = 1;
-
-	mtx_enter(mtx);
-	(*running)++;
-	if ((*running) > 1)
-		rv = 0;
-	mtx_leave(mtx);
-
-	return (rv);
+	return (atomic_inc_int_nv(running) == 1);
 }
 
 int
-scsi_pending_finish(struct mutex *mtx, u_int *running)
+scsi_pending_finish(u_int *running)
 {
-	int rv = 1;
+	if (atomic_cas_uint(running, 1, 0) == 1)
+		return (1);
 
-	mtx_enter(mtx);
-	(*running)--;
-	if ((*running) > 0) {
-		(*running) = 1;
-		rv = 0;
-	}
-	mtx_leave(mtx);
+	*running = 1;
 
-	return (rv);
+	return (0);
 }
 
 void
@@ -409,7 +397,7 @@ scsi_iopool_run(struct scsi_iopool *iopl
 	struct scsi_iohandler *ioh;
 	void *io;
 
-	if (!scsi_pending_start(&iopl->mtx, &iopl->running))
+	if (!scsi_pending_start(&iopl->running))
 		return;
 	do {
 		while (scsi_ioh_pending(iopl)) {
@@ -425,7 +413,7 @@ scsi_iopool_run(struct scsi_iopool *iopl
 
 			ioh->handler(ioh->cookie, io);
 		}
-	} while (!scsi_pending_finish(&iopl->mtx, &iopl->running));
+	} while (!scsi_pending_finish(&iopl->running));
 }
 
 /*
@@ -568,7 +556,7 @@ scsi_xsh_runqueue(struct scsi_link *link
 	struct scsi_iohandler *ioh;
 	int runq;
 
-	if (!scsi_pending_start(&link->pool->mtx, &link->running))
+	if (!scsi_pending_start(&link->running))
 		return;
 	do {
 		runq = 0;
@@ -589,7 +577,7 @@ scsi_xsh_runqueue(struct scsi_link *link
 
 		if (runq)
 			scsi_iopool_run(link->pool);
-	} while (!scsi_pending_finish(&link->pool->mtx, &link->running));
+	} while (!scsi_pending_finish(&link->running));
 }
 
 void
Index: scsiconf.h
===================================================================
RCS file: /cvs/src/sys/scsi/scsiconf.h,v
retrieving revision 1.162
diff -u -p -r1.162 scsiconf.h
--- scsiconf.h	9 Sep 2014 20:30:08 -0000	1.162
+++ scsiconf.h	24 Sep 2014 23:49:56 -0000
@@ -570,8 +570,8 @@ int	scsi_xsh_del(struct scsi_xshandler *
 /*
  * utility functions
  */
-int	scsi_pending_start(struct mutex *, u_int *);
-int	scsi_pending_finish(struct mutex *, u_int *);
+int	scsi_pending_start(u_int *);
+int	scsi_pending_finish(u_int *);
 
 /*
  * Utility functions for SCSI HBA emulation.