diff -r 50813cd186d3 sys/src/9/port/proc.c
--- a/sys/src/9/port/proc.c	Wed Dec 04 22:04:12 2019 +0100
+++ b/sys/src/9/port/proc.c	Thu Dec 05 00:32:32 2019 +0100
@@ -1331,12 +1331,14 @@
 static void
 procflushmmu(int (*match)(Proc*, void*), void *a)
 {
+	char await[MAXMACH];
 	int i, nm, nwait;
 	Proc *p;
 
 	/*
 	 *  tell all matching processes to flush their mmu's
 	 */
+	memset(await, 0, conf.nmach);
 	nwait = 0;
 	for(i=0; i<conf.nproc; i++) {
 		p = &procalloc.arena[i];
@@ -1345,22 +1347,32 @@
 			for(nm = 0; nm < conf.nmach; nm++){
 				if(MACHP(nm)->proc == p){
 					MACHP(nm)->flushmmu = 1;
-					nwait++;
+					if(await[nm] == 0){
+						await[nm] = 1;
+						nwait++;
+					}
 				}
 			}
 		}
 	}
 
-	if(nwait == 0)
-		return;
-
 	/*
 	 *  wait for all other processors to take a clock interrupt
 	 *  and flush their mmu's
 	 */
-	for(nm = 0; nm < conf.nmach; nm++)
-		while(m->machno != nm && MACHP(nm)->flushmmu)
-			sched();
+	for(;;){
+		if(nwait == 0 || nwait == 1 && await[m->machno])
+			break;
+
+		sched();
+
+		for(nm = 0; nm < conf.nmach; nm++){
+			if(await[nm] && MACHP(nm)->flushmmu == 0){
+				await[nm] = 0;
+				nwait--;
+			}
+		}
+	}
 }
 
 static int