Changeset 43669 in vbox for trunk/src/VBox/Main

Timestamp:

Oct 17, 2012 1:20:03 PM (13 years ago)

Author:

vboxsync

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

81452

Message:

Main/MediumImpl: Fix deadlock when two threads attempt to close the same medium object. Triggers lock order violation which is not detectable by the lock validator as only one lock is a RW semaphore, the other one is the AutoCaller event semaphore used for synchronizing callers and init/uninit.

File:

• trunk/src/VBox/Main/src-server/MediumImpl.cpp (modified) (1 diff)

trunk/src/VBox/Main/src-server/MediumImpl.cpp

@@ -4158 +4158 @@
         multilock.release();
         markRegistriesModified();
+        // Release the AutoCalleri now, as otherwise uninit() will simply hang.
+        // Needs to be done before saving the registry, as otherwise there
+        // may be a deadlock with someone else closing this object while we're
+        // in saveModifiedRegistries(), which needs the media tree lock, which
+        // the other thread holds until after uninit() below.
+        /// @todo redesign the locking here, as holding the locks over uninit causes lock order trouble which the lock validator can't detect
+        autoCaller.release();
         m->pVirtualBox->saveModifiedRegistries();
         multilock.acquire();
     }
-
-    // release the AutoCaller, as otherwise uninit() will simply hang
-    autoCaller.release();
+    else
+    {
+        // release the AutoCaller, as otherwise uninit() will simply hang
+        autoCaller.release();
+    }
 
     // Keep the locks held until after uninit, as otherwise the consistency