Changeset 24548

Timestamp:

03/24/08 00:15:42 (2 months ago)

Author:

bonefish

Message:

Applied change proposed in #1917 after encountering the bug the third
time. Releasing the cache's store reference while holding the cache lock
could reverse the usual locking order -- the VFS could potentially call
the remove_vnode() or put_vnode() FS hook, which in turn could use the
file cache, thus resulting in a deadlock. Now we release the store ref
before locking the cache.

Files:

• haiku/trunk/src/system/kernel/vm/vm_cache.cpp (modified) (1 diff)

haiku/trunk/src/system/kernel/vm/vm_cache.cpp

@@ -546 +546 @@
-        ASSERT_LOCKED_MUTEX(&consumer->lock);
-
+        // Remove the store ref before locking the cache. Otherwise we'd call into
+        // the VFS while holding the cache lock, which would reverse the usual
+        // locking order.
+        if (cache->store->ops->release_ref)
+                cache->store->ops->release_ref(cache->store);
+
-        // remove the consumer from the cache, but keep its reference until later
-        mutex_lock(&cache->lock);
-        list_remove_item(&cache->consumers, consumer);
-        consumer->source = NULL;
-
-        if (cache->store->ops->release_ref)
-                cache->store->ops->release_ref(cache->store);
-
-        if (cache->areas == NULL && cache->source != NULL