[PATCH v2 13/22] ntdll: Use shared loader locking in LdrUnloadDll() when possible.

[Paul Gofman]

Signed-off-by: Paul Gofman <pgofman at codeweavers.com>
---
v2:
    - use ldr_data_srw_lock instead of introducing a new one.

 dlls/ntdll/loader.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/dlls/ntdll/loader.c b/dlls/ntdll/loader.c
index 8e2ed03ad4c..5f4f4fea036 100644
--- a/dlls/ntdll/loader.c
+++ b/dlls/ntdll/loader.c
@@ -3858,7 +3858,7 @@ static void free_modref( WINE_MODREF *wm )
  * Remove all unused modrefs and call the internal unloading routines
  * for the library type.
  *
- * The loader must be locked while calling this function.
+ * The loader must be exclusively locked while calling this function.
  */
 static void MODULE_FlushModrefs(void)
 {
@@ -3889,7 +3889,7 @@ static void MODULE_FlushModrefs(void)
 /***********************************************************************
  *           MODULE_DecRefCount
  *
- * The loader must be locked while calling this function.
+ * The loader must be exclusively locked while calling this function.
  */
 static void MODULE_DecRefCount( WINE_MODREF *wm )
 {
@@ -3921,17 +3921,34 @@ static void MODULE_DecRefCount( WINE_MODREF *wm )
 /******************************************************************
  *		LdrUnloadDll (NTDLL.@)
  *
- *
+ * The loader must be unlocked or exclusively locked while calling this function.
  */
 NTSTATUS WINAPI LdrUnloadDll( HMODULE hModule )
 {
     WINE_MODREF *wm;
     NTSTATUS retv = STATUS_SUCCESS;
+    BOOL need_exclusive = FALSE;
 
     if (process_detaching) return retv;
 
     TRACE("(%p)\n", hModule);
 
+    lock_loader_shared();
+    if ((wm = get_modref( hModule )))
+    {
+        RtlAcquireSRWLockExclusive( &ldr_data_srw_lock );
+        if (wm->ldr.LoadCount && wm->ldr.LoadCount != 1)
+        {
+            if (wm->ldr.LoadCount != -1) --wm->ldr.LoadCount;
+        }
+        else if (wm->ldr.LoadCount) need_exclusive = TRUE;
+        /* If the module is already being unloaded LdrUnloadDll() succeeds and doesn't wait. */
+        RtlReleaseSRWLockExclusive( &ldr_data_srw_lock );
+    }
+    else retv = STATUS_DLL_NOT_FOUND;
+    unlock_loader();
+    if (!need_exclusive) return retv;
+
     lock_loader_exclusive();
 
     free_lib_count++;
-- 
2.31.1