[vlc-devel] [PATCH 1/3] os2: implement vlc_once()

[Rémi Denis-Courmont]

IMU, compare-exchange with comparand equal to assignment value makes no sense, since it's just an over-comlicated load.

Le 10 mai 2018 14:41:46 GMT+02:00, KO Myung-Hun <komh78 at gmail.com> a écrit :
>---
> include/vlc_threads.h |  6 ++++++
> src/os2/thread.c      | 20 ++++++++++++++++++++
> 2 files changed, 26 insertions(+)
>
>diff --git a/include/vlc_threads.h b/include/vlc_threads.h
>index 508ddbc001..b0891ac88c 100644
>--- a/include/vlc_threads.h
>+++ b/include/vlc_threads.h
>@@ -125,6 +125,12 @@ typedef struct
> #define VLC_STATIC_COND { NULLHANDLE, 0, NULLHANDLE, 0 }
> #define LIBVLC_NEED_SEMAPHORE
> #define LIBVLC_NEED_RWLOCK
>+typedef struct
>+{
>+    unsigned done;
>+    vlc_mutex_t mutex;
>+} vlc_once_t;
>+#define VLC_STATIC_ONCE { 0, VLC_STATIC_MUTEX }
> typedef struct vlc_threadvar *vlc_threadvar_t;
> typedef struct vlc_timer *vlc_timer_t;
> 
>diff --git a/src/os2/thread.c b/src/os2/thread.c
>index 3b435bfad8..000c3068b3 100644
>--- a/src/os2/thread.c
>+++ b/src/os2/thread.c
>@@ -429,6 +429,26 @@ int vlc_cond_timedwait_daytime (vlc_cond_t
>*p_condvar, vlc_mutex_t *p_mutex,
>     return vlc_cond_wait_common (p_condvar, p_mutex, ulTimeout);
> }
> 
>+void vlc_once(vlc_once_t *once, void (*cb)(void))
>+{
>+    /* once->done is 0 ? */
>+    if( __atomic_cmpxchg32( &once->done, 0, 0 ))
>+    {
>+        vlc_mutex_lock( &once->mutex );
>+
>+        /* still once->done is 0 ? */
>+        if( __atomic_cmpxchg32( &once->done, 0, 0 ))
>+        {
>+            cb();
>+
>+            /* set once->done to 1 */
>+            __atomic_xchg( &once->done, 1 );
>+        }
>+
>+        vlc_mutex_unlock( &once->mutex );
>+    }
>+}
>+
> /*** Thread-specific variables (TLS) ***/
> struct vlc_threadvar
> {
>-- 
>2.13.3
>
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