[Qemu-devel] [PULL 1/1] tests: make filemonitor test more robust to event ordering

["Daniel P. Berrangé" <berrange@redhat.com>]

The ordering of events that are emitted during the rmdir
test have changed with kernel >= 5.3. Semantically both
new & old orderings are correct, so we must be able to
cope with either.

To cope with this, when we see an unexpected event, we
push it back onto the queue and look and the subsequent
event to see if that matches instead.

Tested-by: Peter Xu <peterx@redhat.com>
Tested-by: Wei Yang <richardw.yang@linux.intel.com>
Tested-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 tests/test-util-filemonitor.c | 43 +++++++++++++++++++++++++++--------
 1 file changed, 34 insertions(+), 9 deletions(-)

diff --git a/tests/test-util-filemonitor.c b/tests/test-util-filemonitor.c
index 46e781c022..301cd2db61 100644
--- a/tests/test-util-filemonitor.c
+++ b/tests/test-util-filemonitor.c
@@ -45,6 +45,11 @@ typedef struct {
     const char *filedst;
     int64_t *watchid;
     int eventid;
+    /*
+     * Only valid with OP_EVENT - this event might be
+     * swapped with the next OP_EVENT
+     */
+    bool swapnext;
 } QFileMonitorTestOp;
 
 typedef struct {
@@ -98,6 +103,10 @@ qemu_file_monitor_test_handler(int64_t id,
     QFileMonitorTestData *data = opaque;
     QFileMonitorTestRecord *rec = g_new0(QFileMonitorTestRecord, 1);
 
+    if (debug) {
+        g_printerr("Queue event id %" PRIx64 " event %d file %s\n",
+                   id, event, filename);
+    }
     rec->id = id;
     rec->event = event;
     rec->filename = g_strdup(filename);
@@ -125,7 +134,8 @@ qemu_file_monitor_test_record_free(QFileMonitorTestRecord *rec)
  * to wait for the event to be queued for us.
  */
 static QFileMonitorTestRecord *
-qemu_file_monitor_test_next_record(QFileMonitorTestData *data)
+qemu_file_monitor_test_next_record(QFileMonitorTestData *data,
+                                   QFileMonitorTestRecord *pushback)
 {
     GTimer *timer = g_timer_new();
     QFileMonitorTestRecord *record = NULL;
@@ -139,9 +149,15 @@ qemu_file_monitor_test_next_record(QFileMonitorTestData *data)
     }
     if (data->records) {
         record = data->records->data;
-        tmp = data->records;
-        data->records = g_list_remove_link(data->records, tmp);
-        g_list_free(tmp);
+        if (pushback) {
+            data->records->data = pushback;
+        } else {
+            tmp = data->records;
+            data->records = g_list_remove_link(data->records, tmp);
+            g_list_free(tmp);
+        }
+    } else if (pushback) {
+        qemu_file_monitor_test_record_free(pushback);
     }
     qemu_mutex_unlock(&data->lock);
 
@@ -158,13 +174,15 @@ static bool
 qemu_file_monitor_test_expect(QFileMonitorTestData *data,
                               int64_t id,
                               QFileMonitorEvent event,
-                              const char *filename)
+                              const char *filename,
+                              bool swapnext)
 {
     QFileMonitorTestRecord *rec;
     bool ret = false;
 
-    rec = qemu_file_monitor_test_next_record(data);
+    rec = qemu_file_monitor_test_next_record(data, NULL);
 
+ retry:
     if (!rec) {
         g_printerr("Missing event watch id %" PRIx64 " event %d file %s\n",
                    id, event, filename);
@@ -172,6 +190,11 @@ qemu_file_monitor_test_expect(QFileMonitorTestData *data,
     }
 
     if (id != rec->id) {
+        if (swapnext) {
+            rec = qemu_file_monitor_test_next_record(data, rec);
+            swapnext = false;
+            goto retry;
+        }
         g_printerr("Expected watch id %" PRIx64 " but got %" PRIx64 "\n",
                    id, rec->id);
         goto cleanup;
@@ -347,7 +370,8 @@ test_file_monitor_events(void)
           .filesrc = "fish", },
         { .type = QFILE_MONITOR_TEST_OP_EVENT,
           .filesrc = "", .watchid = &watch4,
-          .eventid = QFILE_MONITOR_EVENT_IGNORED },
+          .eventid = QFILE_MONITOR_EVENT_IGNORED,
+          .swapnext = true },
         { .type = QFILE_MONITOR_TEST_OP_EVENT,
           .filesrc = "fish", .watchid = &watch0,
           .eventid = QFILE_MONITOR_EVENT_DELETED },
@@ -493,8 +517,9 @@ test_file_monitor_events(void)
                 g_printerr("Event id=%" PRIx64 " event=%d file=%s\n",
                            *op->watchid, op->eventid, op->filesrc);
             }
-            if (!qemu_file_monitor_test_expect(
-                    &data, *op->watchid, op->eventid, op->filesrc))
+            if (!qemu_file_monitor_test_expect(&data, *op->watchid,
+                                               op->eventid, op->filesrc,
+                                               op->swapnext))
                 goto cleanup;
             break;
         case QFILE_MONITOR_TEST_OP_CREATE:
-- 
2.21.0