Changes in uspace/lib/c/generic/futex.c [a35b458:063a74b9] in mainline

File:

• uspace/lib/c/generic/futex.c (modified) (2 diffs)

uspace/lib/c/generic/futex.c

@@ -35 +35 @@
 #include <futex.h>
 #include <atomic.h>
+#include <libarch/barrier.h>
+#include <libc.h>
+#include <sys/types.h>
 
 /** Initialize futex counter.
@@ -44 +47 @@
 void futex_initialize(futex_t *futex, int val)
 {
-        atomic_set(&futex->val, val);
+        atomic_set(futex, val);
 }
 
+/** Try to down the futex.
+ *
+ * @param futex Futex.
+ *
+ * @return Non-zero if the futex was acquired.
+ * @return Zero if the futex was not acquired.
+ *
+ */
+int futex_trydown(futex_t *futex)
+{
+        int rc;
 
-#ifdef FUTEX_UPGRADABLE
+        rc = cas(futex, 1, 0);
+        CS_ENTER_BARRIER();
 
-int _upgrade_futexes = 0;
-static futex_t upg_and_wait_futex = FUTEX_INITIALIZER;
-
-void futex_upgrade_all_and_wait(void)
-{
-        futex_down(&upg_and_wait_futex);
-
-        if (!_upgrade_futexes) {
-                rcu_assign(_upgrade_futexes, 1);
-                _rcu_synchronize(BM_BLOCK_THREAD);
-        }
-
-        futex_up(&upg_and_wait_futex);
+        return rc;
 }
 
-#endif
+/** 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.
+ *
+ */
+int futex_down(futex_t *futex)
+{
+        atomic_signed_t nv;
+
+        nv = (atomic_signed_t) atomic_predec(futex);
+        CS_ENTER_BARRIER();
+        if (nv < 0)
+                return __SYSCALL1(SYS_FUTEX_SLEEP, (sysarg_t) &futex->count);
+        
+        return 0;
+}
+
+/** Up the futex.
+ *
+ * @param futex Futex.
+ *
+ * @return ENOENT if there is no such virtual address.
+ * @return Zero in the uncontended case.
+ *
+ */
+int futex_up(futex_t *futex)
+{
+        CS_LEAVE_BARRIER();
+
+        if ((atomic_signed_t) atomic_postinc(futex) < 0)
+                return __SYSCALL1(SYS_FUTEX_WAKEUP, (sysarg_t) &futex->count);
+        
+        return 0;
+}
 
 /** @}