Changeset 52413 in vbox for trunk/src/VBox

Timestamp:

Aug 19, 2014 12:48:42 PM (11 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

95585

Message:

VBoxSVC: resolve undesirable freeze on shutdown.

File:

• trunk/src/VBox/Main/src-all/EventImpl.cpp (modified) (4 diffs)

trunk/src/VBox/Main/src-all/EventImpl.cpp

@@ -579 +579 @@
 
     RTSEMEVENT                    mQEvent;
+    int32_t volatile              mWaitCnt;
     RTCRITSECT                    mcsQLock;
     PassiveQueue                  mQueue;
@@ -725 +726 @@
                                BOOL aActive,
                                EventSource *aOwner) :
-    mActive(aActive), mOwner(aOwner), mRefCnt(0)
+    mActive(aActive), mOwner(aOwner), mWaitCnt(0), mRefCnt(0)
 {
     mListener = aListener;
@@ -882 +883 @@
         // release lock while waiting, listener will not go away due to above holder
         aAlock.release();
+
+        // In order to safely shutdown, count all waiting threads here.
+        ASMAtomicIncS32(&mWaitCnt);
         ::RTSemEventWait(mQEvent, aTimeout);
+        ASMAtomicDecS32(&mWaitCnt);
+
         // reacquire lock
         aAlock.acquire();
@@ -918 +924 @@
         RTSEMEVENT tmp = mQEvent;
         mQEvent = NIL_RTSEMEVENT;
+
+        /* On Darwin it is known that RTSemEventDestroy() returns 0 while
+         * corresponding thread remains to be blocked after that. In order to prevent
+         * undesireble freeze on shutdown, this workaround is used. */
+        Log(("Wait for %d waiters to release.\n", ASMAtomicReadS32(&mWaitCnt)));
+        while (ASMAtomicReadS32(&mWaitCnt) > 0)
+        {
+            ::RTSemEventSignal(tmp);
+
+            /* Are we already done? */
+            if (ASMAtomicReadS32(&mWaitCnt) == 0)
+                break;
+
+            RTThreadSleep(10);
+        }
+        Log(("All waiters just released the lock.\n"));
+
         ::RTSemEventDestroy(tmp);
     }