[PATCH 2/2] ntdll: Pre-check entry->addr before taking a spin lock in RtlWaitOnAddress().

[Paul Gofman]

From: Paul Gofman

---
 dlls/ntdll/sync.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/dlls/ntdll/sync.c b/dlls/ntdll/sync.c
index 1e2019e52c4..3b1e4a721e2 100644
--- a/dlls/ntdll/sync.c
+++ b/dlls/ntdll/sync.c
@@ -907,11 +907,14 @@ NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size

ret = NtWaitForAlertByThreadId( NULL, timeout );

-    spin_lock( &queue->lock );
-    /* We may have already been removed by a call to RtlWakeAddressSingle(). */
+    /* We may have already been removed by a call to RtlWakeAddressSingle() or RtlWakeAddressAll(). */
     if (entry.addr)
-        list_remove( &entry.entry );
-    spin_unlock( &queue->lock );
+    {
+        spin_lock( &queue->lock );
+        if (entry.addr)
+            list_remove( &entry.entry );
+        spin_unlock( &queue->lock );
+    }

TRACE("returning %#lx\n", ret);