Changeset 942 for trunk/src/corelib/io/qfilesystemwatcher_os2.cpp

Timestamp:

Aug 5, 2011, 2:08:17 PM (14 years ago)

Author:

Dmitry A. Kuminov

Message:

OS/2: Fixed native QFileSystemWatcher failure die to bad timings.

It was possible that under the certain CPU load the client (Qt) would
not get its instance of the notification pipe in time and simply fail.

File:

• trunk/src/corelib/io/qfilesystemwatcher_os2.cpp (modified) (1 diff)

trunk/src/corelib/io/qfilesystemwatcher_os2.cpp

@@ -97 +97 @@
     : notifyPipe(NULLHANDLE), eventSem(NULLHANDLE), isRunning(false)
 {
-    ULONG dummy;
-    APIRET arc = DosOpen(PIPE_CHANGENOTIFY, &notifyPipe, &dummy, 0, FILE_OPEN,
-                         OPEN_ACTION_OPEN_IF_EXISTS,
-                         OPEN_SHARE_DENYNONE | OPEN_ACCESS_READONLY, NULL);
+    ULONG dummy, retries = 3;
+    APIRET arc;
+
+    // Try to grab a free pipe instance. Retries are necessary because
+    // DosWaitNPipe() is not "atomic" (even if it returns NO_ERROR, our next
+    // DosOpen() can still fail due to some client being faster). Note that we
+    // wait for max 1000ms on each try because the XWP pipe server may perform
+    // a 1000ms delay between client connections under some circumstances.
+    forever {
+        arc = DosOpen(PIPE_CHANGENOTIFY, &notifyPipe, &dummy, 0, FILE_OPEN,
+                      OPEN_ACTION_OPEN_IF_EXISTS,
+                      OPEN_SHARE_DENYNONE | OPEN_ACCESS_READONLY |
+                      OPEN_FLAGS_NOINHERIT, NULL);
+        if (arc == ERROR_PIPE_BUSY && --retries) {
+            arc = DosWaitNPipe(PIPE_CHANGENOTIFY, 1000);
+            if (arc == NO_ERROR)
+                continue;
+        }
+        break;
+    }
+
     if (arc == NO_ERROR) {
         // make sure the pipe is non-blocking so that we can get ERROR_NO_DATA