Index: sys/sys/proc.h
===================================================================
--- sys/sys/proc.h	(revision 247554)
+++ sys/sys/proc.h	(working copy)
@@ -273,6 +273,7 @@ struct thread {
 	struct vm_map_entry *td_map_def_user; /* (k) Deferred entries. */
 	pid_t		td_dbg_forked;	/* (c) Child pid for debugger. */
 	u_int		td_vp_reserv;	/* (k) Count of reserved vnodes. */
+	u_int		td_no_sleeping;	/* (k) Sleeping disabled count. */
 #define	td_endzero td_sigmask
 
 /* Copied during fork1() or create_thread(). */
@@ -404,7 +405,7 @@ do {									\
 #define	TDP_ALTSTACK	0x00000020 /* Have alternate signal stack. */
 #define	TDP_DEADLKTREAT	0x00000040 /* Lock aquisition - deadlock treatment. */
 #define	TDP_NOFAULTING	0x00000080 /* Do not handle page faults. */
-#define	TDP_NOSLEEPING	0x00000100 /* Thread is not allowed to sleep on a sq. */
+#define	TDP_UNUSED09	0x00000100 /* --available-- */
 #define	TDP_OWEUPC	0x00000200 /* Call addupc() at next AST. */
 #define	TDP_ITHREAD	0x00000400 /* Thread is an interrupt thread. */
 #define	TDP_SYNCIO	0x00000800 /* Local override, disable async i/o. */
@@ -790,17 +791,9 @@ extern pid_t pid_max;
 #define	thread_safetoswapout(td)	((td)->td_flags & TDF_CANSWAP)
 
 /* Control whether or not it is safe for curthread to sleep. */
-#define	THREAD_NO_SLEEPING() do {					\
-	KASSERT(!(curthread->td_pflags & TDP_NOSLEEPING),		\
-	    ("nested no sleeping"));					\
-	curthread->td_pflags |= TDP_NOSLEEPING;				\
-} while (0)
+#define	THREAD_NO_SLEEPING()		(curthread->td_no_sleeping++)
 
-#define	THREAD_SLEEPING_OK() do {					\
-	KASSERT((curthread->td_pflags & TDP_NOSLEEPING),		\
-	    ("nested sleeping ok"));					\
-	curthread->td_pflags &= ~TDP_NOSLEEPING;			\
-} while (0)
+#define	THREAD_SLEEPING_OK()		(curthread->td_no_sleeping--)
 
 #define	PIDHASH(pid)	(&pidhashtbl[(pid) & pidhash])
 extern LIST_HEAD(pidhashhead, proc) *pidhashtbl;
Index: sys/kern/subr_trap.c
===================================================================
--- sys/kern/subr_trap.c	(revision 247554)
+++ sys/kern/subr_trap.c	(working copy)
@@ -158,7 +158,7 @@ userret(struct thread *td, struct trapframe *frame
 	    ("userret: Returning with %d locks held", td->td_locks));
 	KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
 	    ("userret: Returning with pagefaults disabled"));
-	KASSERT((td->td_pflags & TDP_NOSLEEPING) == 0,
+	KASSERT(td->td_no_sleeping == 0,
 	    ("userret: Returning with sleep disabled"));
 	KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
 	    ("userret: Returning with with pinned thread"));
Index: sys/kern/subr_sleepqueue.c
===================================================================
--- sys/kern/subr_sleepqueue.c	(revision 247554)
+++ sys/kern/subr_sleepqueue.c	(working copy)
@@ -296,8 +296,8 @@ sleepq_add(void *wchan, struct lock_object *lock,
 	MPASS((queue >= 0) && (queue < NR_SLEEPQS));
 
 	/* If this thread is not allowed to sleep, die a horrible death. */
-	KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
-	    ("%s: td %p to sleep on wchan %p with TDP_NOSLEEPING on",
+	KASSERT(td->td_no_sleeping == 0,
+	    ("%s: td %p to sleep on wchan %p when sleeps are forbidden",
 	    __func__, td, wchan));
 
 	/* Look up the sleep queue associated with the wait channel 'wchan'. */
Index: sys/dev/mps/mps.c
===================================================================
--- sys/dev/mps/mps.c	(revision 247554)
+++ sys/dev/mps/mps.c	(working copy)
@@ -137,7 +137,7 @@ mps_diag_reset(struct mps_softc *sc,int sleep_flag
 	/*Force NO_SLEEP for threads prohibited to sleep
  	* e.a Thread from interrupt handler are prohibited to sleep.
  	*/	
-	if(curthread->td_pflags & TDP_NOSLEEPING)
+	if(curthread->td_no_sleeping != 0)
 		sleep_flag = NO_SLEEP;
  
 	/* Push the magic sequence */
@@ -470,7 +470,7 @@ mps_request_sync(struct mps_softc *sc, void *req,
 	int i, count, ioc_sz, residual;
 	int sleep_flags = CAN_SLEEP;
 	
-	if(curthread->td_pflags & TDP_NOSLEEPING)
+	if(curthread->td_no_sleeping != 0)
 		sleep_flags = NO_SLEEP;
 
 	/* Step 1 */