branches/5.1:

Fix Bug#36819 ut_usectime does not handle errors from gettimeofday

by retrying gettimeofday() several times if it fails in ut_usectime().
If it fails on all calls then return error to the caller to be handled
at higher level.

Update the variable innodb_row_lock_time_max in SHOW STATUS output only
if ut_usectime() was successful.

include/ut0ut.h

@@ -145,11 +145,15 @@ ib_time_t
 ut_time(void);
 /*=========*/
 /**************************************************************
-Returns system time. */
+Returns system time.
+Upon successful completion, the value 0 is returned; otherwise the
+value -1 is returned and the global variable errno is set to indicate the
+error. */
 
-void
+int
 ut_usectime(
 /*========*/
+			/* out: 0 on success, -1 otherwise */
 	ulint*	sec,	/* out: seconds since the Epoch */
 	ulint*	ms);	/* out: microseconds since the Epoch+*sec */
 /**************************************************************

srv/srv0srv.c

@@ -1453,8 +1453,11 @@ srv_suspend_mysql_thread(
 		srv_n_lock_wait_count++;
 		srv_n_lock_wait_current_count++;
 
-		ut_usectime(&sec, &ms);
-		start_time = (ib_longlong)sec * 1000000 + ms;
+		if (ut_usectime(&sec, &ms) == -1) {
+			start_time = -1;
+		} else {
+			start_time = (ib_longlong)sec * 1000000 + ms;
+		}
 	}
 	/* Wake the lock timeout monitor thread, if it is suspended */
 
@@ -1508,14 +1511,20 @@ srv_suspend_mysql_thread(
 	wait_time = ut_difftime(ut_time(), slot->suspend_time);
 
 	if (thr->lock_state == QUE_THR_LOCK_ROW) {
-		ut_usectime(&sec, &ms);
-		finish_time = (ib_longlong)sec * 1000000 + ms;
+		if (ut_usectime(&sec, &ms) == -1) {
+			finish_time = -1;
+		} else {
+			finish_time = (ib_longlong)sec * 1000000 + ms;
+		}
 
 		diff_time = (ulint) (finish_time - start_time);
 
 		srv_n_lock_wait_current_count--;
 		srv_n_lock_wait_time = srv_n_lock_wait_time + diff_time;
-		if (diff_time > srv_n_lock_max_wait_time) {
+		if (diff_time > srv_n_lock_max_wait_time &&
+		    /* only update the variable if we successfully
+		    retrieved the start and finish times. See Bug#36819. */
+		    start_time != -1 && finish_time != -1) {
 			srv_n_lock_max_wait_time = diff_time;
 		}
 	}

ut/ut0ut.c

@@ -112,19 +112,45 @@ ut_time(void)
 }
 
 /**************************************************************
-Returns system time. */
+Returns system time.
+Upon successful completion, the value 0 is returned; otherwise the
+value -1 is returned and the global variable errno is set to indicate the
+error. */
 
-void
+int
 ut_usectime(
 /*========*/
+			/* out: 0 on success, -1 otherwise */
 	ulint*	sec,	/* out: seconds since the Epoch */
 	ulint*	ms)	/* out: microseconds since the Epoch+*sec */
 {
 	struct timeval	tv;
+	int		ret;
+	int		errno_gettimeofday;
+	int		i;
+
+	for (i = 0; i < 10; i++) {
+
+		ret = ut_gettimeofday(&tv, NULL);
+
+		if (ret == -1) {
+			errno_gettimeofday = errno;
+			ut_print_timestamp(stderr);
+			fprintf(stderr, "  InnoDB: gettimeofday(): %s\n",
+				strerror(errno_gettimeofday));
+			os_thread_sleep(100000);  /* 0.1 sec */
+			errno = errno_gettimeofday;
+		} else {
+			break;
+		}
+	}
+
+	if (ret != -1) {
+		*sec = (ulint) tv.tv_sec;
+		*ms  = (ulint) tv.tv_usec;
+	}
 
-	ut_gettimeofday(&tv, NULL);
-	*sec = (ulint) tv.tv_sec;
-	*ms  = (ulint) tv.tv_usec;
+	return(ret);
 }
 
 /**************************************************************