Index: sys/kern/subr_syscall.c
===================================================================
--- sys/kern/subr_syscall.c
+++ sys/kern/subr_syscall.c
@@ -70,11 +70,9 @@
 	if (__predict_false(td->td_cowgen != p->p_cowgen))
 		thread_cow_update(td);
 	traced = (p->p_flag & P_TRACED) != 0;
-	if (__predict_false(traced || td->td_dbgflags & TDB_USERWR)) {
+	if (__predict_false(traced)) {
 		PROC_LOCK(p);
-		td->td_dbgflags &= ~TDB_USERWR;
-		if (traced)
-			td->td_dbgflags |= TDB_SCE;
+		td->td_dbgflags |= TDB_SCE;
 		PROC_UNLOCK(p);
 	}
 	error = (p->p_sysent->sv_fetch_syscall_args)(td);
Index: sys/kern/subr_trap.c
===================================================================
--- sys/kern/subr_trap.c
+++ sys/kern/subr_trap.c
@@ -228,6 +228,7 @@
 	flags = td->td_flags;
 	td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
 	    TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
+	td->td_dbgflags &= ~TDB_USERWR;
 	thread_unlock(td);
 	VM_CNT_INC(v_trap);
 
Index: sys/kern/sys_process.c
===================================================================
--- sys/kern/sys_process.c
+++ sys/kern/sys_process.c
@@ -1037,6 +1037,13 @@
 				    p->p_pid, data);
 			p->p_ptevents = 0;
 			FOREACH_THREAD_IN_PROC(p, td3) {
+				/*
+				 * Request AST to clear TDB_USERWR.
+				 */
+				thread_lock(td3);
+				td3->td_flags |= TDF_ASTPENDING;
+				thread_unlock(td3);
+
 				if ((td3->td_dbgflags & TDB_FSTP) != 0) {
 					sigqueue_delete(&td3->td_sigqueue,
 					    SIGSTOP);