[atomic] Provide mutex-based ptr cmpxchg

To handle those CPUs where we do not have an atomic cmpxchg.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/cairo-atomic.c b/src/cairo-atomic.c
index c569000cb..777ba5cdf 100644
--- a/src/cairo-atomic.c
+++ b/src/cairo-atomic.c
@@ -71,6 +71,19 @@ _cairo_atomic_int_cmpxchg (int *x, int oldv, int newv)
     return ret;
 }
 
+void *
+_cairo_atomic_ptr_cmpxchg (void **x, void *oldv, void *newv)
+{
+    void *ret;
+
+    CAIRO_MUTEX_LOCK (_cairo_atomic_mutex);
+    ret = *x;
+    if (ret == oldv)
+	*x = newv;
+    CAIRO_MUTEX_UNLOCK (_cairo_atomic_mutex);
+
+    return ret;
+}
 #endif
 
 #ifdef ATOMIC_OP_NEEDS_MEMORY_BARRIER