[newlib-cygwin] Cygwin: authz: Use dedicated locks per datastructure

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=2e03e5a040af42e0bbc5fc019d478889f0b9e9b0

commit 2e03e5a040af42e0bbc5fc019d478889f0b9e9b0
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Mon Aug 22 14:25:05 2022 +0200

    Cygwin: authz: Use dedicated locks per datastructure
    
    So far we use a single muto to guard three different datastructures
    inside class authz_ctx: the authz HANDLE, the user context HANDLE
    and the context cache list.  Split the single muto into three
    independent SRWLOCKs and guard all datastrcutures as necessary to
    avoid thread contention.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/sec/helper.cc | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/winsup/cygwin/sec/helper.cc b/winsup/cygwin/sec/helper.cc
index 750631b2b..45bf65dac 100644
--- a/winsup/cygwin/sec/helper.cc
+++ b/winsup/cygwin/sec/helper.cc
@@ -707,7 +707,18 @@ _everyone_sd (void *buf, ACCESS_MASK access)
   return psd;
 }
 
-static NO_COPY muto authz_guard;
+static NO_COPY SRWLOCK authz_lock = SRWLOCK_INIT;
+#define AUTHZ_LOCK()    (AcquireSRWLockExclusive (&authz_lock))
+#define AUTHZ_UNLOCK()  (ReleaseSRWLockExclusive (&authz_lock))
+
+static NO_COPY SRWLOCK user_ctx_lock = SRWLOCK_INIT;
+#define USER_CTX_LOCK()    (AcquireSRWLockExclusive (&user_ctx_lock))
+#define USER_CTX_UNLOCK()  (ReleaseSRWLockExclusive (&user_ctx_lock))
+
+static NO_COPY SRWLOCK slist_lock = SRWLOCK_INIT;
+#define SLIST_LOCK()    (AcquireSRWLockExclusive (&slist_lock))
+#define SLIST_UNLOCK()  (ReleaseSRWLockExclusive (&slist_lock))
+
 static LUID authz_dummy_luid = { 0 };
 
 class authz_ctx_cache_entry
@@ -766,13 +777,13 @@ authz_ctx::operator AUTHZ_RESOURCE_MANAGER_HANDLE ()
   if (!authz_hdl)
     {
       /* Create handle to Authz resource manager */
-      authz_guard.init ("authz_guard")->acquire ();
+      AUTHZ_LOCK ();
       if (!authz_hdl
 	  && !AuthzInitializeResourceManager (AUTHZ_RM_FLAG_NO_AUDIT,
 					      NULL, NULL, NULL, NULL,
 					      &authz_hdl))
 	debug_printf ("AuthzInitializeResourceManager, %E");
-      authz_guard.release ();
+      AUTHZ_UNLOCK ();
     }
   return authz_hdl;
 }
@@ -805,9 +816,9 @@ authz_ctx_cache::context (PSID user_sid)
   else
     {
       entry->set (user_sid, ctx_hdl);
-      authz_guard.acquire ();
+      SLIST_LOCK ();
       SLIST_INSERT_HEAD (&ctx_list, entry, ctx_next);
-      authz_guard.release ();
+      SLIST_UNLOCK ();
       return entry->context ();
     }
   delete entry;
@@ -830,7 +841,7 @@ authz_ctx::get_user_attribute (mode_t *attribute, PSECURITY_DESCRIPTOR psd,
       /* Avoid lock in default case. */
       if (!user_ctx_hdl)
 	{
-	  authz_guard.acquire ();
+	  USER_CTX_LOCK ();
 	  /* Check user_ctx_hdl again under lock to avoid overwriting
 	     user_ctx_hdl if it has already been initialized. */
 	  if (!user_ctx_hdl
@@ -838,7 +849,7 @@ authz_ctx::get_user_attribute (mode_t *attribute, PSECURITY_DESCRIPTOR psd,
 						   authz_dummy_luid, NULL,
 						   &user_ctx_hdl))
 	    debug_printf ("AuthzInitializeContextFromToken, %E");
-	  authz_guard.release ();
+	  USER_CTX_UNLOCK ();
 	}
       if (user_ctx_hdl)
 	ctx_hdl = user_ctx_hdl;