Changeset 62170 in vbox for trunk/src/libs

Timestamp:

Jul 11, 2016 6:14:11 PM (8 years ago)

Author:

vboxsync

Message:

XPCOM: Change the shutdown order in nsExceptionService, attempting to fix a sporadic crash. The biggest change is postponing the lock freeing to the destructor. The order change of the operations in the Shutdown method eliminates the concerns mention in the ThreadDestruct method. The change in DoDropThread is pure paranoia, intended to avoid potential crashes due to continuing with a NULL pointer in *emp if the thread is not known.

File:

• trunk/src/libs/xpcom18a4/xpcom/base/nsExceptionService.cpp (modified) (7 diffs)

trunk/src/libs/xpcom18a4/xpcom/base/nsExceptionService.cpp

@@ -84 +84 @@
 #ifdef NS_DEBUG
   inline nsrefcnt ReleaseQuiet() {
-    // shut up NS_ASSERT_OWNINGTHREAD (see explaination below)
+    // shut up NS_ASSERT_OWNINGTHREAD (see explanation below)
     nsAutoOwningThread old = _mOwningThread;
     _mOwningThread = nsAutoOwningThread();
@@ -115 +115 @@
 // holding objects (i.e. it's thread-safe to call them), but
 // NS_CheckThreadSafe() assertions will still happen and yell in the debug
-// build. Since it is quite annoying, we use a special ReleaseQuiet() mehtod
+// build. Since it is quite annoying, we use a special ReleaseQuiet() method
 // in DoDropThread() to shut them up.
 NS_IMPL_THREADSAFE_ISUPPORTS1(nsExceptionManager, nsIExceptionManager)
@@ -165 +165 @@
 
 PRUintn nsExceptionService::tlsIndex = BAD_TLS_INDEX;
-PRLock *nsExceptionService::lock = PR_FALSE;
+PRLock *nsExceptionService::lock = nsnull;
 nsExceptionManager *nsExceptionService::firstThread = nsnull;
 
@@ -201 +201 @@
 {
   Shutdown();
+  if (lock) {
+    PRLock *tmp = lock;
+    lock = nsnull;
+    PR_DestroyLock(tmp);
+  }
   /* destructor code */
 #ifdef NS_DEBUG
@@ -211 +216 @@
 {
   if (!lock) {
-    // a typical situation is when IPC worker threads that have instantiated
-    // exception managers are stopped after nsExceptionService is shut down,
-    // which will result into this warning.  disable it.
-#if 0    
     NS_WARNING("nsExceptionService ignoring thread destruction after shutdown");
-#endif    
     return;
   }
@@ -225 +225 @@
 void nsExceptionService::Shutdown()
 {
+  PR_SetThreadPrivate(tlsIndex, nsnull);
   mProviders.Reset();
   if (lock) {
     DropAllThreads();
-    PR_DestroyLock(lock);
-    lock = nsnull;
-  }
-  PR_SetThreadPrivate(tlsIndex, nsnull);
+  }
 }
 
@@ -356 +354 @@
     nsExceptionManager **emp = &firstThread;
     while (*emp != thread) {
-        NS_ABORT_IF_FALSE(*emp, "Could not find the thread to drop!");
+        if (!*emp)
+        {
+            NS_WARNING("Could not find the thread to drop!");
+            return;
+        }
         emp = &(*emp)->mNextThread;
     }
     *emp = thread->mNextThread;
     thread->ReleaseQuiet();
-    thread = 0;
+    thread = nsnull;
 }