Index: sys/kern/kern_fork.c
===================================================================
--- sys/kern/kern_fork.c
+++ sys/kern/kern_fork.c
@@ -1081,7 +1081,7 @@
 			proc_reparent(p, dbg);
 			sx_xunlock(&proctree_lock);
 			td->td_dbgflags |= TDB_CHILD | TDB_SCX | TDB_FSTP;
-			ptracestop(td, SIGSTOP);
+			ptracestop(td, SIGSTOP, NULL);
 			td->td_dbgflags &= ~(TDB_CHILD | TDB_SCX);
 		} else {
 			/*
@@ -1102,7 +1102,7 @@
 		_STOPEVENT(p, S_SCX, td->td_dbg_sc_code);
 		if ((p->p_ptevents & PTRACE_SCX) != 0 ||
 		    (td->td_dbgflags & TDB_BORN) != 0)
-			ptracestop(td, SIGTRAP);
+			ptracestop(td, SIGTRAP, NULL);
 		td->td_dbgflags &= ~(TDB_SCX | TDB_BORN);
 		PROC_UNLOCK(p);
 	}
Index: sys/kern/kern_sig.c
===================================================================
--- sys/kern/kern_sig.c
+++ sys/kern/kern_sig.c
@@ -2500,10 +2500,11 @@
 	return (wakeup_swapper);
 }
 
-int
-ptracestop(struct thread *td, int sig)
+void
+ptracestop(struct thread *td, int sig, int *newsig)
 {
 	struct proc *p = td->td_proc;
+	ksiginfo_t ksi;
 
 	PROC_LOCK_ASSERT(p, MA_OWNED);
 	KASSERT(!(p->p_flag & P_WEXIT), ("Stopping exiting process"));
@@ -2523,8 +2524,8 @@
 			 * events when the process exits.
 			 */
 			td->td_dbgflags &= ~TDB_XSIG;
-			PROC_SUNLOCK(p);
-			return (sig);
+			td->td_xsig = sig;
+			break;
 		}
 
 		/*
@@ -2563,7 +2564,18 @@
 		}
 	}
 	PROC_SUNLOCK(p);
-	return (td->td_xsig);
+	if (newsig)
+		*newsig = td->td_xsig;
+	else if (td->td_xsig) {
+		/*
+		 * Caller is not prepared to deliver a debugger requested
+		 * signal. We must queue it up for handling next ast.
+		 */
+		ksiginfo_init(&ksi);
+		ksi.ksi_flags |= KSI_HEAD;
+		ksi.ksi_signo = td->td_xsig;
+		tdksignal(td, td->td_xsig, &ksi);
+	}
 }
 
 static void
@@ -2783,7 +2795,16 @@
 			}
 
 			mtx_unlock(&ps->ps_mtx);
-			newsig = ptracestop(td, sig);
+			if (td->td_xsig)
+				/*
+				 * This signal is from a previous call to
+				 * ptracestop() that was unable to deliver
+				 * it.
+				 */
+				newsig = td->td_xsig;
+			else
+				ptracestop(td, sig, &newsig);
+			td->td_xsig = 0;
 			mtx_lock(&ps->ps_mtx);
 
 			if (sig != newsig) {
Index: sys/kern/kern_thr.c
===================================================================
--- sys/kern/kern_thr.c
+++ sys/kern/kern_thr.c
@@ -356,7 +356,7 @@
 	p->p_pendingexits++;
 	td->td_dbgflags |= TDB_EXIT;
 	if (p->p_ptevents & PTRACE_LWP)
-		ptracestop(td, SIGTRAP);
+		ptracestop(td, SIGTRAP, NULL);
 	PROC_UNLOCK(p);
 	tidhash_remove(td);
 	PROC_LOCK(p);
Index: sys/kern/subr_syscall.c
===================================================================
--- sys/kern/subr_syscall.c
+++ sys/kern/subr_syscall.c
@@ -88,7 +88,7 @@
 			td->td_dbg_sc_code = sa->code;
 			td->td_dbg_sc_narg = sa->narg;
 			if (p->p_ptevents & PTRACE_SCE)
-				ptracestop((td), SIGTRAP);
+				ptracestop((td), SIGTRAP, NULL);
 			PROC_UNLOCK(p);
 		}
 		if (td->td_dbgflags & TDB_USERWR) {
@@ -222,7 +222,7 @@
 		if (traced &&
 		    ((td->td_dbgflags & (TDB_FORK | TDB_EXEC)) != 0 ||
 		    (p->p_ptevents & PTRACE_SCX) != 0))
-			ptracestop(td, SIGTRAP);
+			ptracestop(td, SIGTRAP, NULL);
 		td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
 		PROC_UNLOCK(p);
 	}
@@ -259,7 +259,7 @@
 		if (td->td_dbgflags & TDB_VFORK) {
 			PROC_LOCK(p);
 			if (p->p_ptevents & PTRACE_VFORK)
-				ptracestop(td, SIGTRAP);
+				ptracestop(td, SIGTRAP, NULL);
 			td->td_dbgflags &= ~TDB_VFORK;
 			PROC_UNLOCK(p);
 		}
Index: sys/sys/signalvar.h
===================================================================
--- sys/sys/signalvar.h
+++ sys/sys/signalvar.h
@@ -370,7 +370,7 @@
 void	pgsignal(struct pgrp *pgrp, int sig, int checkctty, ksiginfo_t *ksi);
 int	postsig(int sig);
 void	kern_psignal(struct proc *p, int sig);
-int	ptracestop(struct thread *td, int sig);
+void	ptracestop(struct thread *td, int sig, int *newsig);
 void	sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *retmask);
 struct sigacts *sigacts_alloc(void);
 void	sigacts_copy(struct sigacts *dest, struct sigacts *src);