Changeset 36292 in vbox

Timestamp:

Mar 16, 2011 12:45:59 PM (14 years ago)

Author:

vboxsync

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

70589

Message:

VD: Fix possible race condition which can lead to hanging I/O requests

File:

• trunk/src/VBox/Storage/VD.cpp (modified) (2 diffs)

trunk/src/VBox/Storage/VD.cpp

@@ -3475 +3475 @@
                                   size_t cbCompleted)
 {
+    PVDIO    pVDIo = (PVDIO)pvUser;
+    PVBOXHDD pDisk = pVDIo->pDisk;
+
+    /*
+     * Grab the disk critical section to avoid races with other threads which
+     * might still modify the I/O context.
+     * Example is that iSCSI is doing an asynchronous write but calls us already
+     * while the other thread is still hanging in vdWriteHelperAsync and couldn't update
+     * the fBlocked state yet.
+     * It can overwrite the state to true before we call vdIoCtxContinue and the
+     * the request would hang indefinite.
+     */
+    int rc = RTCritSectEnter(&pDisk->CritSect);
+    AssertRC(rc);
+
     /* Continue */
     pIoCtx->fBlocked = false;
@@ -3483 +3498 @@
     if (!pIoCtx->cbTransferLeft)
         pIoCtx->pfnIoCtxTransfer = NULL;
+
+    rc = RTCritSectLeave(&pDisk->CritSect);
+    AssertRC(rc);
 
     vdIoCtxContinue(pIoCtx, rcReq);