Index: kern/kern_kse.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_kse.c,v
retrieving revision 1.223
diff -u -r1.223 kern_kse.c
--- kern/kern_kse.c	22 Feb 2006 18:57:49 -0000	1.223
+++ kern/kern_kse.c	19 May 2006 14:19:17 -0000
@@ -1088,7 +1088,7 @@
 	/* Let the new thread become owner of the upcall */
 	ku->ku_owner   = td2;
 	td2->td_upcall = ku;
-	td2->td_flags  = 0;
+	td2->td_flags  = TDF_NEEDSUSPCHK;
 	td2->td_pflags = TDP_SA|TDP_UPCALLING;
 	td2->td_state  = TDS_CAN_RUN;
 	td2->td_inhibitors = 0;
Index: kern/kern_sig.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_sig.c,v
retrieving revision 1.331
diff -u -r1.331 kern_sig.c
--- kern/kern_sig.c	12 May 2006 05:04:44 -0000	1.331
+++ kern/kern_sig.c	19 May 2006 14:19:21 -0000
@@ -2434,6 +2434,7 @@
 	mtx_assert(&sched_lock, MA_OWNED);
 
 	FOREACH_THREAD_IN_PROC(p, td2) {
+		td2->td_flags |= TDF_NEEDSUSPCHK;
 		if ((TD_IS_SLEEPING(td2) || TD_IS_SWAPPED(td2)) &&
 		    (td2->td_flags & TDF_SINTR) &&
 		    !TD_IS_SUSPENDED(td2)) {
Index: kern/kern_thr.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_thr.c,v
retrieving revision 1.43
diff -u -r1.43 kern_thr.c
--- kern/kern_thr.c	17 Apr 2006 18:20:37 -0000	1.43
+++ kern/kern_thr.c	19 May 2006 14:19:22 -0000
@@ -246,6 +246,7 @@
 	if (linkkg)
 		sched_fork_ksegrp(td, newkg);
 	sched_fork_thread(td, newtd);
+	newtd->td_flags |= TDF_NEEDSUSPCHK;
 	TD_SET_CAN_RUN(newtd);
 	/* if ((flags & THR_SUSPENDED) == 0) */
 		setrunqueue(newtd, SRQ_BORING);
Index: kern/kern_thread.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_thread.c,v
retrieving revision 1.233
diff -u -r1.233 kern_thread.c
--- kern/kern_thread.c	21 Mar 2006 10:05:15 -0000	1.233
+++ kern/kern_thread.c	19 May 2006 14:19:22 -0000
@@ -770,6 +770,7 @@
 		if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
 			goto stopme;
 		FOREACH_THREAD_IN_PROC(p, td2) {
+			td2->td_flags |= TDF_NEEDSUSPCHK;
 			if (td2 == td)
 				continue;
 			td2->td_flags |= TDF_ASTPENDING;
@@ -901,6 +902,7 @@
 	p = td->td_proc;
 	mtx_assert(&Giant, MA_NOTOWNED);
 	PROC_LOCK_ASSERT(p, MA_OWNED);
+	mtx_lock_spin(&sched_lock);
 	while (P_SHOULDSTOP(p) ||
 	      ((p->p_flag & P_TRACED) && (td->td_flags & TDF_DBSUSPEND))) {
 		if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
@@ -912,22 +914,30 @@
 			 * XXX Should be safe to access unlocked
 			 * as it can only be set to be true by us.
 			 */
-			if (p->p_singlethread == td)
+			if (p->p_singlethread == td) {
+				mtx_unlock_spin(&sched_lock);
 				return (0);	/* Exempt from stopping. */
+			}
 		}
-		if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
+		if ((p->p_flag & P_SINGLE_EXIT) && return_instead) {
+			mtx_unlock_spin(&sched_lock);
 			return (EINTR);
+		}
 
 		/* Should we goto user boundary if we didn't come from there? */
 		if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
-		    (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
+		    (p->p_flag & P_SINGLE_BOUNDARY) && return_instead) {
+			mtx_unlock_spin(&sched_lock);
 			return (ERESTART);
+		}
 
 		/* If thread will exit, flush its pending signals */
-		if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td))
+		if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
+			mtx_unlock_spin(&sched_lock);
 			sigqueue_flush(&td->td_sigqueue);
+			mtx_lock_spin(&sched_lock);
+		}
 
-		mtx_lock_spin(&sched_lock);
 		thread_stopped(p);
 		/*
 		 * If the process is waiting for us to exit,
@@ -959,7 +969,10 @@
 		}
 		mtx_unlock_spin(&sched_lock);
 		PROC_LOCK(p);
+		mtx_lock_spin(&sched_lock);
 	}
+	td->td_flags &= ~TDF_NEEDSUSPCHK;
+	mtx_unlock_spin(&sched_lock);
 	return (0);
 }
 
Index: kern/subr_sleepqueue.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/subr_sleepqueue.c,v
retrieving revision 1.29
diff -u -r1.29 subr_sleepqueue.c
--- kern/subr_sleepqueue.c	21 Apr 2006 20:40:43 -0000	1.29
+++ kern/subr_sleepqueue.c	19 May 2006 14:19:23 -0000
@@ -368,6 +368,18 @@
 		(void *)td, (long)p->p_pid, p->p_comm);
 
 	MPASS(td->td_flags & TDF_SINTR);
+
+	mtx_lock_spin(&sched_lock);
+	/*
+	 * Check if there is suspension request, signal or KSE interrupt,
+	 * if none of these events happened, just return, in most time,
+	 * it is true, and we save lots of cycles.
+	 */
+	if (!(td->td_flags & (TDF_NEEDSUSPCHK|TDF_NEEDSIGCHK|TDF_INTERRUPT)))
+		return (0);	/* return with scheduler lock held. */
+
+	/* Slow path, check every thing. */
+	mtx_unlock_spin(&sched_lock);
 	mtx_unlock_spin(&sc->sc_lock);
 
 	/* See if there are any pending signals for this thread. */
Index: kern/subr_trap.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/subr_trap.c,v
retrieving revision 1.286
diff -u -r1.286 subr_trap.c
--- kern/subr_trap.c	10 Feb 2006 14:59:16 -0000	1.286
+++ kern/subr_trap.c	19 May 2006 14:19:23 -0000
@@ -188,8 +188,7 @@
 	if (p->p_sflag & PS_MACPEND)
 		p->p_sflag &= ~PS_MACPEND;
 #endif
-	td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK |
-	    TDF_NEEDRESCHED | TDF_INTERRUPT);
+	td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDRESCHED | TDF_INTERRUPT);
 	cnt.v_soft++;
 	mtx_unlock_spin(&sched_lock);
 
@@ -264,6 +263,9 @@
 #endif
 	}
 	if (flags & TDF_NEEDSIGCHK) {
+		mtx_lock_spin(&sched_lock);
+		td->td_flags &= ~TDF_NEEDSIGCHK;
+		mtx_unlock_spin(&sched_lock);
 		PROC_LOCK(p);
 		mtx_lock(&p->p_sigacts->ps_mtx);
 		while ((sig = cursig(td)) != 0)
Index: sys/proc.h
===================================================================
RCS file: /home/ncvs/src/sys/sys/proc.h,v
retrieving revision 1.458
diff -u -r1.458 proc.h
--- sys/proc.h	18 May 2006 08:43:46 -0000	1.458
+++ sys/proc.h	19 May 2006 14:19:33 -0000
@@ -351,7 +351,7 @@
 #define	TDF_TIMOFAIL	0x00001000 /* Timeout from sleep after we were awake. */
 #define	TDF_INTERRUPT	0x00002000 /* Thread is marked as interrupted. */
 #define	TDF_UNUSED14	0x00004000 /* --available -- */
-#define	TDF_UNUSED15	0x00008000 /* --available -- */
+#define	TDF_NEEDSUSPCHK	0x00008000 /* Thread should check job control flags. */
 #define	TDF_NEEDRESCHED	0x00010000 /* Thread needs to yield. */
 #define	TDF_NEEDSIGCHK	0x00020000 /* Thread may need signal delivery. */
 #define	TDF_XSIG	0x00040000 /* Thread is exchanging signal under trace */