1 files changed, 43 insertions, 11 deletions

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 9c52707..e28bdc4 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -2364,6 +2364,13 @@ tdsigwakeup(struct thread *td, int sig, sig_t action, int intrval)
 		}
 
 		/*
+		 * Don't awaken a sleeping thread for SIGSTOP if the
+		 * STOP signal is deferred.
+		 */
+		if ((prop & SA_STOP) && (td->td_flags & TDF_SBDRY))
+			goto out;
+
+		/*
 		 * Give low priority threads a better chance to run.
 		 */
 		if (td->td_priority > PUSER)
@@ -2404,12 +2411,13 @@ sig_suspend_threads(struct thread *td, struct proc *p, int sending)
 		if ((TD_IS_SLEEPING(td2) || TD_IS_SWAPPED(td2)) &&
 		    (td2->td_flags & TDF_SINTR)) {
 			if (td2->td_flags & TDF_SBDRY) {
-				if (TD_IS_SUSPENDED(td2))
-					wakeup_swapper |=
-					    thread_unsuspend_one(td2);
-				if (TD_ON_SLEEPQ(td2))
-					wakeup_swapper |=
-					    sleepq_abort(td2, ERESTART);
+				/*
+				 * Once a thread is asleep with
+				 * TDF_SBDRY set, it should never
+				 * become suspended due to this check.
+				 */
+				KASSERT(!TD_IS_SUSPENDED(td2),
+				    ("thread with deferred stops suspended"));
 			} else if (!TD_IS_SUSPENDED(td2)) {
 				thread_suspend_one(td2);
 			}
@@ -2529,6 +2537,34 @@ tdsigcleanup(struct thread *td)
 
 }
 
+/* Defer the delivery of SIGSTOP for the current thread. */
+void
+sigdeferstop(struct thread *td)
+{
+
+	KASSERT(!(td->td_flags & TDF_SBDRY),
+	    ("attempt to set TDF_SBDRY recursively"));
+	thread_lock(td);
+	td->td_flags |= TDF_SBDRY;
+	thread_unlock(td);
+}
+
+/*
+ * Permit the delivery of SIGSTOP for the current thread.  This does
+ * not immediately suspend if a stop was posted.  Instead, the thread
+ * will suspend either via ast() or a subsequent interruptible sleep.
+ */
+void
+sigallowstop(struct thread *td)
+{
+
+	KASSERT(td->td_flags & TDF_SBDRY,
+	    ("attempt to clear already-cleared TDF_SBDRY"));
+	thread_lock(td);
+	td->td_flags &= ~TDF_SBDRY;
+	thread_unlock(td);
+}
+
 /*
  * If the current process has received a signal (should be caught or cause
  * termination, should interrupt current syscall), return the signal number.
@@ -2561,7 +2597,7 @@ issignal(struct thread *td, int stop_allowed)
 		SIGSETOR(sigpending, p->p_sigqueue.sq_signals);
 		SIGSETNAND(sigpending, td->td_sigmask);
 
-		if (p->p_flag & P_PPWAIT)
+		if (p->p_flag & P_PPWAIT || td->td_flags & TDF_SBDRY)
 			SIG_STOPSIGMASK(sigpending);
 		if (SIGISEMPTY(sigpending))	/* no signal to send */
 			return (0);
@@ -2677,10 +2713,6 @@ issignal(struct thread *td, int stop_allowed)
 				    (p->p_pgrp->pg_jobc == 0 &&
 				     prop & SA_TTYSTOP))
 					break;	/* == ignore */
-
-				/* Ignore, but do not drop the stop signal. */
-				if (stop_allowed != SIG_STOP_ALLOWED)
-					return (sig);
 				mtx_unlock(&ps->ps_mtx);
 				WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK,
 				    &p->p_mtx.lock_object, "Catching SIGSTOP");