[PATCH 2/2] ntdll: Use a CS to ensure that RtlWaitOnAddress compares and queues atomically.

[Zebediah Figura]

Currently a wake may occur between calling compare_addr() and performing the
select request; in that case the thread will never be woken. Prevent this by
taking a CS around both operations.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=46099
Signed-off-by: Zebediah Figura 
---
 dlls/ntdll/sync.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/dlls/ntdll/sync.c b/dlls/ntdll/sync.c
index e1a48d7044..62cb3cd5ec 100644
--- a/dlls/ntdll/sync.c
+++ b/dlls/ntdll/sync.c
@@ -1961,6 +1961,15 @@ NTSTATUS WINAPI RtlSleepConditionVariableSRW( RTL_CONDITION_VARIABLE *variable,
     return status;
 }

+static RTL_CRITICAL_SECTION addr_section;
+static RTL_CRITICAL_SECTION_DEBUG addr_section_debug =
+{
+    0, 0, &addr_section,
+    { &addr_section_debug.ProcessLocksList, &addr_section_debug.ProcessLocksList },
+      0, 0, { (DWORD_PTR)(__FILE__ ": addr_section") }
+};
+static RTL_CRITICAL_SECTION addr_section = { &addr_section_debug, -1, 0, 0, 0, 0 };
+
 static BOOL compare_addr( const void *addr, const void *cmp, SIZE_T size )
 {
     switch (size)
@@ -2004,8 +2013,12 @@ NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size

for (;;)
     {
+        RtlEnterCriticalSection( &addr_section );
         if (!compare_addr( addr, cmp, size ))
+        {
+            RtlLeaveCriticalSection( &addr_section );
             return STATUS_SUCCESS;
+        }

SERVER_START_REQ( select )
         {
@@ -2021,6 +2034,9 @@ NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size
             call        = reply->call;
         }
         SERVER_END_REQ;
+
+        RtlLeaveCriticalSection( &addr_section );
+
         if (ret == STATUS_PENDING) ret = wait_select_reply( &cookie );
         if (ret != STATUS_USER_APC) break;
         if (invoke_apc( &call, &result ))
@@ -2043,7 +2059,9 @@ NTSTATUS WINAPI RtlWaitOnAddress( const void *addr, const void *cmp, SIZE_T size
  */
 void WINAPI RtlWakeAddressAll( const void *addr )
 {
+    RtlEnterCriticalSection( &addr_section );
     while (NtReleaseKeyedEvent( 0, addr, 0, &zero_timeout ) == STATUS_SUCCESS) {}
+    RtlLeaveCriticalSection( &addr_section );
 }

/***********************************************************************
@@ -2051,5 +2069,7 @@ void WINAPI RtlWakeAddressAll( const void *addr )
  */
 void WINAPI RtlWakeAddressSingle( const void *addr )
 {
+    RtlEnterCriticalSection( &addr_section );
     NtReleaseKeyedEvent( 0, addr, 0, &zero_timeout );
+    RtlLeaveCriticalSection( &addr_section );
 }