Changeset 56087 in vbox for trunk/src/VBox/Devices

Timestamp:

May 27, 2015 8:42:10 AM (10 years ago)

Author:

vboxsync

Message:

Storage/AHCI: Fix race condition which might lead to a hang during power off

File:

• trunk/src/VBox/Devices/Storage/DevAHCI.cpp (modified) (4 diffs)

trunk/src/VBox/Devices/Storage/DevAHCI.cpp

@@ -2024 +2024 @@
     Assert(fAllTasksCanceled);
 
+    Assert(pAhciPort->cTasksActive == 0);
+
     pAhciPort->regIS   = 0;
     pAhciPort->regIE   = 0;
@@ -2053 +2055 @@
     pAhciPort->u32QueuedTasksFinished = 0;
     pAhciPort->u32CurrentCommandSlot = 0;
-
-    pAhciPort->cTasksActive = 0;
 
     ASMAtomicWriteU32(&pAhciPort->MediaEventStatus, ATA_EVENT_STATUS_UNCHANGED);
@@ -6012 +6012 @@
     bool fXchg = ASMAtomicCmpXchgPtr(&pAhciPort->aActiveTasks[pAhciReq->uTag], NULL, pAhciReq);
 
-    if (fXchg)
-    {
-        AssertReleaseMsg(ASMAtomicReadU32(&pAhciPort->cTasksActive) > 0,
-                         ("Inconsistent request counter\n"));
-        ASMAtomicDecU32(&pAhciPort->cTasksActive);
-    }
-
     /*
      * Leave a release log entry if the request was active for more than 25 seconds
@@ -6188 +6181 @@
                         pAhciReq->cbTransfer, rcReq));
          }
+    }
+
+    /*
+     * Decrement the active task counter as the last step or we might run into a
+     * hang during power off otherwise (see @bugref{7859}).
+     * Before it could happen that we signal PDM that we are done while we still have to
+     * copy the data to the guest but EMT might be busy destroying the driver chains
+     * below us while we have to delegate copying data to EMT instead of doing it
+     * on this thread.
+     */
+    if (fXchg)
+    {
+        AssertReleaseMsg(ASMAtomicReadU32(&pAhciPort->cTasksActive) > 0,
+                         ("Inconsistent request counter\n"));
+        ASMAtomicDecU32(&pAhciPort->cTasksActive);
     }