[cairo-commit] 2 commits - src/cairo-mutex.c src/cairo-mutex-private.h

[GitLab Mirror]

 src/cairo-mutex-private.h |    2 +-
 src/cairo-mutex.c         |   41 ++++++++++++++++++++++++++++++++++-------
 2 files changed, 35 insertions(+), 8 deletions(-)

New commits:
commit 0d7e0dcb175fd24e32600cb9cf0d97845a0c727f
Merge: 9831eba0e 46e538ddb
Author: Adrian Johnson <ajohnson at redneon.com>
Date:   Sat May 27 10:20:57 2023 +0000

    Merge branch 'issue-782' into 'master'
    
    Use a spinlock to prevent race condition when initializing mutexes
    
    Closes #782
    
    See merge request cairo/cairo!478

commit 46e538ddbbf5ad02cb6a9d5ff4a483ba63660dc5
Author: Adrian Johnson <ajohnson at redneon.com>
Date:   Sat May 27 17:59:21 2023 +0930

    Use a spinlock to prevent race condition when initializing mutexes
    
    Fixes #782

diff --git a/src/cairo-mutex-private.h b/src/cairo-mutex-private.h
index 61a7160a0..65732a180 100644
--- a/src/cairo-mutex-private.h
+++ b/src/cairo-mutex-private.h
@@ -53,7 +53,7 @@ cairo_private void _cairo_mutex_finalize (void);
 #endif
 /* only if using static initializer and/or finalizer define the boolean */
 #if _CAIRO_MUTEX_IMPL_USE_STATIC_INITIALIZER || _CAIRO_MUTEX_IMPL_USE_STATIC_FINALIZER
-  cairo_private extern cairo_bool_t _cairo_mutex_initialized;
+  cairo_private extern int _cairo_mutex_initialized;
 #endif
 
 /* Finally, extern the static mutexes and undef */
diff --git a/src/cairo-mutex.c b/src/cairo-mutex.c
index 0a31dced3..5b6debeca 100644
--- a/src/cairo-mutex.c
+++ b/src/cairo-mutex.c
@@ -41,13 +41,17 @@
 
 #if _CAIRO_MUTEX_IMPL_USE_STATIC_INITIALIZER || _CAIRO_MUTEX_IMPL_USE_STATIC_FINALIZER
 
+#define _CAIRO_MUTEX_UNINITIALIZED 0
+#define _CAIRO_MUTEX_INITIALIZING  1
+#define _CAIRO_MUTEX_INITIALIZED   2
+
 # if _CAIRO_MUTEX_IMPL_USE_STATIC_INITIALIZER
-#  define _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VALUE FALSE
+#  define _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VALUE _CAIRO_MUTEX_UNINITIALIZED
 # else
-#  define _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VALUE TRUE
+#  define _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VALUE _CAIRO_MUTEX_INITIALIZED
 # endif
 
-cairo_bool_t _cairo_mutex_initialized = _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VALUE;
+int _cairo_mutex_initialized = _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VALUE;
 
 # undef _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VALUE
 
@@ -56,24 +60,47 @@ cairo_bool_t _cairo_mutex_initialized = _CAIRO_MUTEX_IMPL_INITIALIZED_DEFAULT_VA
 #if _CAIRO_MUTEX_IMPL_USE_STATIC_INITIALIZER
 void _cairo_mutex_initialize (void)
 {
-    if (_cairo_mutex_initialized)
+#if HAS_ATOMIC_OPS
+    int old_value;
+    do {
+        old_value = _cairo_atomic_int_cmpxchg_return_old (&_cairo_mutex_initialized,
+                                                          _CAIRO_MUTEX_UNINITIALIZED,
+                                                          _CAIRO_MUTEX_INITIALIZING);
+        if (old_value == _CAIRO_MUTEX_INITIALIZED)
+            return;
+
+    } while (old_value == _CAIRO_MUTEX_INITIALIZING);
+#else
+    if (_cairo_mutex_initialized == _CAIRO_MUTEX_INITIALIZED)
         return;
 
-    _cairo_mutex_initialized = TRUE;
+    _cairo_mutex_initialized = _CAIRO_MUTEX_INITIALIZED;
+#endif
 
 #define  CAIRO_MUTEX_DECLARE(mutex) CAIRO_MUTEX_INIT (mutex);
 #include "cairo-mutex-list-private.h"
 #undef   CAIRO_MUTEX_DECLARE
+
+#if HAS_ATOMIC_OPS
+    _cairo_atomic_int_set_relaxed (&_cairo_mutex_initialized, _CAIRO_MUTEX_INITIALIZED);
+#endif
 }
 #endif
 
 #if _CAIRO_MUTEX_IMPL_USE_STATIC_FINALIZER
 void _cairo_mutex_finalize (void)
 {
-    if (!_cairo_mutex_initialized)
+#if HAS_ATOMIC_OPS
+    if (!_cairo_atomic_int_cmpxchg (&_cairo_mutex_initialized,
+                                    _CAIRO_MUTEX_INITIALIZED,
+                                    _CAIRO_MUTEX_UNINITIALIZED))
+        return;
+#else
+    if (_cairo_mutex_initialized != _CAIRO_MUTEX_INITIALIZED)
         return;
 
-    _cairo_mutex_initialized = FALSE;
+    _cairo_mutex_initialized = _CAIRO_MUTEX_UNINITIALIZED;
+#endif
 
 #define  CAIRO_MUTEX_DECLARE(mutex) CAIRO_MUTEX_FINI (mutex);
 #include "cairo-mutex-list-private.h"