windows-smb-dead-vc-gc-20080627

LICENSE MIT

When an SMB virtual circuit is prematurely closed due to an error
condition by one thread it is possible that there are still several
other threads still using the VC which will determine that the VC
is dead shortly.  As a result we maintain a dead vc list to ensure
that dead vcs are not destroyed while still in use.

With the addition of locking though this causes a problem because the
locks allocated to the virtual circuit are not freed until the vc is
destroyed.

This patch reworks the cleanup routine to make the freeing of resources
the responsibility of the release routine when the refcount hits 0
and the VC is marked dead.

diff --git a/src/WINNT/afsd/smb.c b/src/WINNT/afsd/smb.c
index f073b81..0aa88bb 100644 (file)
--- a/src/WINNT/afsd/smb.c
+++ b/src/WINNT/afsd/smb.c
@@ -947,6 +947,18 @@ void smb_ReleaseVCInternal(smb_vc_t *vcp)
              */
             vcp->refCount++;
         }
+    } else if (vcp->flags & SMB_VCFLAG_ALREADYDEAD) {
+        /* The reference count is non-zero but the VC is dead.
+         * This implies that some FIDs, TIDs, etc on the VC have yet to 
+         * be cleaned up.  Add a reference that will be dropped by
+         * smb_CleanupDeadVC() and try to cleanup the VC again.
+         * Eventually the refCount will drop to zero when all of the
+         * active threads working with the VC end their task.
+         */
+        vcp->refCount++;        /* put the refCount back */
+        lock_ReleaseWrite(&smb_rctLock);
+        smb_CleanupDeadVC(vcp);
+        lock_ObtainWrite(&smb_rctLock);
     }
 }
 
@@ -1065,10 +1077,14 @@ void smb_CleanupDeadVC(smb_vc_t *vcp)
        uidpNext = vcp->usersp;
     }
 
+    lock_ObtainMutex(&vcp->mx);
+    vcp->flags &= ~SMB_VCFLAG_CLEAN_IN_PROGRESS;
+    lock_ReleaseMutex(&vcp->mx);
+
     /* The vcp is now on the deadVCsp list.  We intentionally drop the
      * reference so that the refcount can reach 0 and we can delete it */
     smb_ReleaseVCNoLock(vcp);
-    
+
     lock_ReleaseWrite(&smb_rctLock);
     osi_Log1(smb_logp, "Finished cleaning up dead vcp 0x%x", vcp);
 }