Changes in uspace/lib/c/include/futex.h [9d58539:156b6406] in mainline

File:

• uspace/lib/c/include/futex.h (modified) (1 diff)

uspace/lib/c/include/futex.h

@@ -38 +38 @@
 #include <atomic.h>
 #include <sys/types.h>
+#include <libc.h>
 
-#define FUTEX_INITIALIZER  {1}
+typedef struct futex {
+        atomic_t val;
+#ifdef FUTEX_UPGRADABLE
+        int upgraded;
+#endif
+} futex_t;
 
-typedef atomic_t futex_t;
 
 extern void futex_initialize(futex_t *futex, int value);
-extern int futex_down(futex_t *futex);
-extern int futex_trydown(futex_t *futex);
-extern int futex_up(futex_t *futex);
+
+#ifdef FUTEX_UPGRADABLE
+#include <rcu.h>
+
+#define FUTEX_INITIALIZE(val) {{ (val) }, 0}
+
+#define futex_lock(fut) \
+({ \
+        rcu_read_lock(); \
+        (fut)->upgraded = rcu_access(_upgrade_futexes); \
+        if ((fut)->upgraded) \
+                (void) futex_down((fut)); \
+})
+
+#define futex_trylock(fut) \
+({ \
+        rcu_read_lock(); \
+        int _upgraded = rcu_access(_upgrade_futexes); \
+        if (_upgraded) { \
+                int _acquired = futex_trydown((fut)); \
+                if (!_acquired) { \
+                        rcu_read_unlock(); \
+                } else { \
+                        (fut)->upgraded = true; \
+                } \
+                _acquired; \
+        } else { \
+                (fut)->upgraded = false; \
+                1; \
+        } \
+})
+                
+#define futex_unlock(fut) \
+({ \
+        if ((fut)->upgraded) \
+                (void) futex_up((fut)); \
+        rcu_read_unlock(); \
+})
+
+extern int _upgrade_futexes;
+
+extern void futex_upgrade_all_and_wait(void);
+                
+#else
+
+#define FUTEX_INITIALIZE(val) {{ (val) }}
+
+#define futex_lock(fut)     (void) futex_down((fut))
+#define futex_trylock(fut)  futex_trydown((fut))
+#define futex_unlock(fut)   (void) futex_up((fut))
+                
+#endif
+
+#define FUTEX_INITIALIZER     FUTEX_INITIALIZE(1)
+
+/** Try to down the futex.
+ *
+ * @param futex Futex.
+ *
+ * @return Non-zero if the futex was acquired.
+ * @return Zero if the futex was not acquired.
+ *
+ */
+static inline int futex_trydown(futex_t *futex)
+{
+        return cas(&futex->val, 1, 0);
+}
+
+/** Down the futex.
+ *
+ * @param futex Futex.
+ *
+ * @return ENOENT if there is no such virtual address.
+ * @return Zero in the uncontended case.
+ * @return Otherwise one of ESYNCH_OK_ATOMIC or ESYNCH_OK_BLOCKED.
+ *
+ */
+static inline int futex_down(futex_t *futex)
+{
+        if ((atomic_signed_t) atomic_predec(&futex->val) < 0)
+                return __SYSCALL1(SYS_FUTEX_SLEEP, (sysarg_t) &futex->val.count);
+        
+        return 0;
+}
+
+/** Up the futex.
+ *
+ * @param futex Futex.
+ *
+ * @return ENOENT if there is no such virtual address.
+ * @return Zero in the uncontended case.
+ *
+ */
+static inline int futex_up(futex_t *futex)
+{
+        if ((atomic_signed_t) atomic_postinc(&futex->val) < 0)
+                return __SYSCALL1(SYS_FUTEX_WAKEUP, (sysarg_t) &futex->val.count);
+        
+        return 0;
+}
 
 #endif