* VMCache: Added a UserData attribute which can be used by the lock holder.

* Added "bool consumerLocked" parameter to VMCache::Unlock() and
  ReleaseRefAndUnlock(). Since Unlock() may cause the cache to be merged with
  a consumer cache, the flag is needed to prevent a deadlock in case the
  caller still holds a lock to the consumer. Hasn't been a problem yet, since
  that situation never occurred.
* VMCacheChainLocker: Reversed unlocking order to bottom-up. The other
  direction could cause a deadlock in case caches would be merged, since the
  locking order would be reversed. The way VMCacheChainLocker was used this
  didn't happen, though.
* fault_get_page(): While copying a page from a lower cache to the top cache,
  we do now unlock all caches but the top one, so we don't unnecessarily
  kill concurrency.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@35153 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/vm/VMCache.h

@@ -74,14 +74,15 @@ public:
 	inline	bool				TryLock();
 	inline	bool				SwitchLock(mutex* from);
 	inline	bool				SwitchFromReadLock(rw_lock* from);
-			void				Unlock();
+			void				Unlock(bool consumerLocked = false);
 	inline	void				AssertLocked();
 
 	inline	void				AcquireRefLocked();
 	inline	void				AcquireRef();
 	inline	void				ReleaseRefLocked();
 	inline	void				ReleaseRef();
-	inline	void				ReleaseRefAndUnlock();
+	inline	void				ReleaseRefAndUnlock(
+									bool consumerLocked = false);
 
 			void				WaitForPageEvents(vm_page* page, uint32 events,
 									bool relock);
@@ -108,6 +109,11 @@ public:
 
 			status_t			FlushAndRemoveAllPages();
 
+			void*				UserData()	{ return fUserData; }
+			void				SetUserData(void* data)	{ fUserData = data; }
+									// Settable by the lock owner and valid as
+									// long as the lock is owned.
+
 			// for debugging only
 			mutex*				GetLock()
 									{ return &fLock; }
@@ -171,13 +177,14 @@ private:
 
 	inline	bool				_IsMergeable() const;
 
-			void				_MergeWithOnlyConsumer();
+			void				_MergeWithOnlyConsumer(bool consumerLocked);
 			void				_RemoveConsumer(VMCache* consumer);
 
 private:
 			int32				fRefCount;
 			mutex				fLock;
 			PageEventWaiter*	fPageEventWaiters;
+			void*				fUserData;
 };
 
 
@@ -272,10 +279,10 @@ VMCache::ReleaseRef()
 
 
 void
-VMCache::ReleaseRefAndUnlock()
+VMCache::ReleaseRefAndUnlock(bool consumerLocked)
 {
 	ReleaseRefLocked();
-	Unlock();
+	Unlock(consumerLocked);
 }