From: Jeffrey Altman <jaltman@your-file-system.com>
Date: Fri, 19 Oct 2012 15:26:21 +0000 (-0400)
Subject: Windows: ObjectInfo RefCount 0 <-> 1 transitions
X-Git-Tag: upstream/1.8.0_pre1^2~1880
X-Git-Url: https://git.michaelhowe.org/gitweb/?a=commitdiff_plain;h=5857dd36b2b129fd2cf187650723b896c24f5177;p=packages%2Fo%2Fopenafs.git

Windows: ObjectInfo RefCount 0 <-> 1 transitions

When the reference count transitions from 0 <-> 1 ensure that the
ObjectInfoLock is held exclusive to prevent the current thread from
altering the state while another thread is holding the ObjectInfoLock
shared in order to conditionally perform an action based upon
the the reference count being zero.

Change-Id: I5bcf384a0ea90e4896e55b537e92112ac3791a4c
Reviewed-on: http://gerrit.openafs.org/8257
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
---

diff --git a/src/WINNT/afsrdr/kernel/lib/AFSGeneric.cpp b/src/WINNT/afsrdr/kernel/lib/AFSGeneric.cpp
index fc85688c0..6a7a9388d 100644
--- a/src/WINNT/afsrdr/kernel/lib/AFSGeneric.cpp
+++ b/src/WINNT/afsrdr/kernel/lib/AFSGeneric.cpp
@@ -6543,10 +6543,31 @@ AFSObjectInfoIncrement( IN AFSObjectInfoCB *ObjectInfo)
 
     LONG lCount;
 
-    AFSAcquireShared( &ObjectInfo->NonPagedInfo->ObjectInfoLock,
-                      TRUE);
+    if ( ObjectInfo->ObjectReferenceCount == 0)
+    {
+
+        AFSAcquireExcl( &ObjectInfo->NonPagedInfo->ObjectInfoLock,
+                        TRUE);
+
+        lCount = InterlockedIncrement( &ObjectInfo->ObjectReferenceCount);
+    }
+    else
+    {
+
+        AFSAcquireShared( &ObjectInfo->NonPagedInfo->ObjectInfoLock,
+                          TRUE);
+
+        lCount = InterlockedIncrement( &ObjectInfo->ObjectReferenceCount);
+
+        if ( lCount == 1)
+        {
 
-    lCount = InterlockedIncrement( &ObjectInfo->ObjectReferenceCount);
+            AFSReleaseResource( &ObjectInfo->NonPagedInfo->ObjectInfoLock);
+
+            AFSAcquireExcl( &ObjectInfo->NonPagedInfo->ObjectInfoLock,
+                            TRUE);
+        }
+    }
 
     AFSReleaseResource( &ObjectInfo->NonPagedInfo->ObjectInfoLock);
 
@@ -6564,6 +6585,19 @@ AFSObjectInfoDecrement( IN AFSObjectInfoCB *ObjectInfo)
 
     lCount = InterlockedDecrement( &ObjectInfo->ObjectReferenceCount);
 
+    if ( lCount == 0)
+    {
+
+        lCount = InterlockedIncrement( &ObjectInfo->ObjectReferenceCount);
+
+        AFSReleaseResource(&ObjectInfo->NonPagedInfo->ObjectInfoLock);
+
+        AFSAcquireExcl( &ObjectInfo->NonPagedInfo->ObjectInfoLock,
+                        TRUE);
+
+        lCount = InterlockedDecrement( &ObjectInfo->ObjectReferenceCount);
+    }
+
     AFSReleaseResource( &ObjectInfo->NonPagedInfo->ObjectInfoLock);
 
     return lCount;