[waffle] [PATCH v2 2/3] wcore: rework non-compatible mutex initialization

[Emil Velikov]

C11 does not specify a static initializer, based on the idea that the
a mutex will be platform and/or implementation dependent. As such the
alternative solution is to initialize the mutex with call_once/mtx_init.
This will allow us to remove the transition hack, and in due time move
to the system's C11 threads implementation.

v2: Actually use call_once() to prevent the possibility of multiple
threads hitting the mtx_init() at the same time. Suggested by Jose.

Cc: Jose Fonseca <jfonseca at vmware.com>
Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
---
 src/waffle/core/wcore_display.c | 19 ++++++++++++++++++-
 src/waffle/core/wcore_display.h |  9 ++-------
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/waffle/core/wcore_display.c b/src/waffle/core/wcore_display.c
index 2feeeba..2cf0dcd 100644
--- a/src/waffle/core/wcore_display.c
+++ b/src/waffle/core/wcore_display.c
@@ -29,16 +29,25 @@
 
 #include "wcore_display.h"
 
+static mtx_t mutex;
+
+static void
+wcore_display_init_once(void)
+{
+    mtx_init(&mutex, mtx_plain);
+}
+
 bool
 wcore_display_init(struct wcore_display *self,
                    struct wcore_platform *platform)
 {
     static size_t id_counter = 0;
-    static mtx_t mutex = _MTX_INITIALIZER_NP;
+    static once_flag flag = ONCE_FLAG_INIT;
 
     assert(self);
     assert(platform);
 
+    call_once(&flag, wcore_display_init_once);
     mtx_lock(&mutex);
     self->api.display_id = ++id_counter;
     mtx_unlock(&mutex);
@@ -52,3 +61,11 @@ wcore_display_init(struct wcore_display *self,
 
     return true;
 }
+
+bool
+wcore_display_teardown(struct wcore_display *self)
+{
+    assert(self);
+    mtx_destroy(&mutex);
+    return true;
+}
diff --git a/src/waffle/core/wcore_display.h b/src/waffle/core/wcore_display.h
index de6ca5e..6d95d98 100644
--- a/src/waffle/core/wcore_display.h
+++ b/src/waffle/core/wcore_display.h
@@ -56,10 +56,5 @@ wcore_display_init(struct wcore_display *self,
                    struct wcore_platform *platform);
 
 
-static inline bool
-wcore_display_teardown(struct wcore_display *self)
-{
-    (void) self;
-    assert(self);
-    return true;
-}
+bool
+wcore_display_teardown(struct wcore_display *self);
-- 
2.3.1