[ovs-dev] [PATCH] timeval: Add "time/stop" unixctl command, for use in unit tests.

[Ben Pfaff]

Although we try to avoid it, some unit tests are necessarily
timing-sensitive.  The new "time/stop" command that this commit adds should
help with that, by preventing time from advancing from the viewpoint of
the OVS "timeval" functions except when "time/warp" explicitly advances
the current time.  This should allow the unit tests that need it to become
reproducible regardless of the speed at which the tests run.

This commit adds one unit of "time/stop" to the unit test suite, in the one
timing-sensitive test of which I am currently aware.

Bug #9782.
Reported-by: Tim Chen <tchen at nicira.com>
Signed-off-by: Ben Pfaff <blp at nicira.com>
---
 lib/timeval.c         |   41 +++++++++++++++++++++++++++++++----------
 tests/ofproto-dpif.at |    1 +
 2 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/lib/timeval.c b/lib/timeval.c
index 35819ed..3f12b50 100644
--- a/lib/timeval.c
+++ b/lib/timeval.c
@@ -54,8 +54,9 @@ static struct timespec monotonic_time;
 /* The monotonic time at which the time module was initialized. */
 static long long int boot_time;
 
-/* Fixed monotonic time offset, for use by unit tests. */
-static struct timespec warp_offset;
+/* features for use by unit tests. */
+static struct timespec warp_offset; /* Offset added to monotonic_time. */
+static bool time_stopped;           /* Disables real-time updates, if true. */
 
 /* Time at which to die with SIGALRM (if not TIME_MIN). */
 static time_t deadline = TIME_MIN;
@@ -183,15 +184,17 @@ refresh_monotonic(void)
 {
     time_init();
 
-    if (monotonic_clock == CLOCK_MONOTONIC) {
-        clock_gettime(monotonic_clock, &monotonic_time);
-    } else {
-        refresh_wall_if_ticked();
-        monotonic_time = wall_time;
-    }
-    timespec_add(&monotonic_time, &monotonic_time, &warp_offset);
+    if (!time_stopped) {
+        if (monotonic_clock == CLOCK_MONOTONIC) {
+            clock_gettime(monotonic_clock, &monotonic_time);
+        } else {
+            refresh_wall_if_ticked();
+            monotonic_time = wall_time;
+        }
+        timespec_add(&monotonic_time, &monotonic_time, &warp_offset);
 
-    monotonic_tick = false;
+        monotonic_tick = false;
+    }
 }
 
 /* Forces a refresh of the current time from the kernel.  It is not usually
@@ -561,6 +564,22 @@ get_cpu_usage(void)
 
 /* Unixctl interface. */
 
+/* "time/stop" stops the monotonic time returned by e.g. time_msec() from
+ * advancing, except due to later calls to "time/warp". */
+static void
+timeval_stop_cb(struct unixctl_conn *conn,
+                 int argc OVS_UNUSED, const char *argv[] OVS_UNUSED,
+                 void *aux OVS_UNUSED)
+{
+    time_stopped = true;
+    unixctl_command_reply(conn, NULL);
+}
+
+/* "time/warp MSECS" advances the current monotonic time by the specified
+ * number of milliseconds.  Unless "time/stop" has also been executed, the
+ * monotonic clock continues to tick forward at the normal rate afterward.
+ *
+ * Does not affect wall clock readings. */
 static void
 timeval_warp_cb(struct unixctl_conn *conn,
                 int argc OVS_UNUSED, const char *argv[], void *aux OVS_UNUSED)
@@ -577,12 +596,14 @@ timeval_warp_cb(struct unixctl_conn *conn,
     ts.tv_sec = msecs / 1000;
     ts.tv_nsec = (msecs % 1000) * 1000 * 1000;
     timespec_add(&warp_offset, &warp_offset, &ts);
+    timespec_add(&monotonic_time, &monotonic_time, &ts);
     unixctl_command_reply(conn, "warped");
 }
 
 void
 timeval_dummy_register(void)
 {
+    unixctl_command_register("time/stop", "", 0, 0, timeval_stop_cb, NULL);
     unixctl_command_register("time/warp", "MSECS", 1, 1,
                              timeval_warp_cb, NULL);
 }
diff --git a/tests/ofproto-dpif.at b/tests/ofproto-dpif.at
index a3f32c0..a306c11 100644
--- a/tests/ofproto-dpif.at
+++ b/tests/ofproto-dpif.at
@@ -983,6 +983,7 @@ OVS_VSWITCHD_START(
 
 AT_CHECK([test-netflow --detach --pidfile $NETFLOW_PORT:127.0.0.1 > netflow.log])AT_CAPTURE_FILE([netflow.log])
 
+AT_CHECK([ovs-appctl time/stop])
 n=1
 while test $n -le 60; do
     n=`expr $n + 1`
-- 
1.7.2.5