- Add a new td flag TDF_NEEDSUSPCHK that is set whenever a thread needs

   to enter thread_suspend_check().
 - Set TDF_ASTPENDING along with TDF_NEEDSUSPCHK so we can move the
   thread_suspend_check() to ast() rather than userret().
 - Check TDF_NEEDSUSPCHK in the sleepq_catch_signals() optimization so
   that we don't miss a suspend request.  If this is set use the
   expensive signal path.
 - Set NEEDSUSPCHK when creating a new thread in thr in case the
   creating thread is due to be suspended as well but has not yet.

Reviewed by:	davidxu (Authored original patch)

5 files changed, 18 insertions, 19 deletions

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index eee71f1..6fc597b 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -2286,6 +2286,7 @@ sig_suspend_threads(struct thread *td, struct proc *p, int sending)
 
 	FOREACH_THREAD_IN_PROC(p, td2) {
 		thread_lock(td2);
+		td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
 		if ((TD_IS_SLEEPING(td2) || TD_IS_SWAPPED(td2)) &&
 		    (td2->td_flags & TDF_SINTR) &&
 		    !TD_IS_SUSPENDED(td2)) {
diff --git a/sys/kern/kern_thr.c b/sys/kern/kern_thr.c
index 3d410b5..61d9a88 100644
--- a/sys/kern/kern_thr.c
+++ b/sys/kern/kern_thr.c
@@ -235,6 +235,8 @@ create_thread(struct thread *td, mcontext_t *ctx,
 	/* let the scheduler know about these things. */
 	sched_fork_thread(td, newtd);
 	thread_unlock(td);
+	if (P_SHOULDSTOP(p))
+		newtd->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
 	PROC_UNLOCK(p);
 	thread_lock(newtd);
 	if (rtp != NULL) {
diff --git a/sys/kern/kern_thread.c b/sys/kern/kern_thread.c
index 65fdae4..8745e5e 100644
--- a/sys/kern/kern_thread.c
+++ b/sys/kern/kern_thread.c
@@ -549,7 +549,7 @@ thread_single(int mode)
 			if (td2 == td)
 				continue;
 			thread_lock(td2);
-			td2->td_flags |= TDF_ASTPENDING;
+			td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
 			if (TD_IS_INHIBITED(td2)) {
 				switch (mode) {
 				case SINGLE_EXIT:
@@ -751,6 +751,7 @@ thread_suspend_switch(struct thread *td)
 	p->p_suspcount++;
 	PROC_UNLOCK(p);
 	thread_lock(td);
+	td->td_flags &= ~TDF_NEEDSUSPCHK;
 	TD_SET_SUSPENDED(td);
 	sched_sleep(td, 0);
 	PROC_SUNLOCK(p);
@@ -771,6 +772,7 @@ thread_suspend_one(struct thread *td)
 	THREAD_LOCK_ASSERT(td, MA_OWNED);
 	KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 	p->p_suspcount++;
+	td->td_flags &= ~TDF_NEEDSUSPCHK;
 	TD_SET_SUSPENDED(td);
 	sched_sleep(td, 0);
 }
diff --git a/sys/kern/subr_sleepqueue.c b/sys/kern/subr_sleepqueue.c
index e12ef6e..bc3f1d8 100644
--- a/sys/kern/subr_sleepqueue.c
+++ b/sys/kern/subr_sleepqueue.c
@@ -391,7 +391,7 @@ sleepq_catch_signals(void *wchan, int pri)
 	 * directly.
 	 */
 	thread_lock(td);
-	if ((td->td_flags & TDF_NEEDSIGCHK) == 0) {
+	if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
 		sleepq_switch(wchan, pri);
 		return (0);
 	}
diff --git a/sys/kern/subr_trap.c b/sys/kern/subr_trap.c
index 1701fba..a92abd2 100644
--- a/sys/kern/subr_trap.c
+++ b/sys/kern/subr_trap.c
@@ -96,11 +96,9 @@ userret(struct thread *td, struct trapframe *frame)
 	thread_unlock(td);
 	PROC_UNLOCK(p);
 #endif
-
 #ifdef KTRACE
 	KTRUSERRET(td);
 #endif
-
 	/*
 	 * If this thread tickled GEOM, we need to wait for the giggling to
 	 * stop before we return to userland
@@ -109,21 +107,9 @@ userret(struct thread *td, struct trapframe *frame)
 		g_waitidle();
 
 	/*
-	 * We need to check to see if we have to exit or wait due to a
-	 * single threading requirement or some other STOP condition.
-	 * Don't bother doing all the work if the stop bits are not set
-	 * at this time.. If we miss it, we miss it.. no big deal.
-	 */
-	if (P_SHOULDSTOP(p)) {
-		PROC_LOCK(p);
-		thread_suspend_check(0);	/* Can suspend or kill */
-		PROC_UNLOCK(p);
-	}
-	/*
 	 * Charge system time if profiling.
 	 */
 	if (p->p_flag & P_PROFIL) {
-
 		addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
 	}
 	/*
@@ -172,9 +158,8 @@ ast(struct trapframe *framep)
 	 */
 	thread_lock(td);
 	flags = td->td_flags;
-	td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK |
-	    TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND |
-	    TDF_MACPEND);
+	td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
+	    TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
 	thread_unlock(td);
 	PCPU_INC(cnt.v_trap);
 
@@ -242,6 +227,15 @@ ast(struct trapframe *framep)
 		mtx_unlock(&p->p_sigacts->ps_mtx);
 		PROC_UNLOCK(p);
 	}
+	/*
+	 * We need to check to see if we have to exit or wait due to a
+	 * single threading requirement or some other STOP condition.
+	 */
+	if (flags & TDF_NEEDSUSPCHK) {
+		PROC_LOCK(p);
+		thread_suspend_check(0);
+		PROC_UNLOCK(p);
+	}
 
 	userret(td, framep);
 	mtx_assert(&Giant, MA_NOTOWNED);