Cleanup: Re-organise source dir

[userspace-rcu.git] / include / urcu / futex.h

diff --git a/include/urcu/futex.h b/include/urcu/futex.h
new file mode 100644 (file)
index 0000000..0486ff6
--- /dev/null
+++ b/include/urcu/futex.h
@@ -0,0 +1,125 @@
+#ifndef _URCU_FUTEX_H
+#define _URCU_FUTEX_H
+
+/*
+ * urcu-futex.h
+ *
+ * Userspace RCU - sys_futex/compat_futex header.
+ *
+ * Copyright 2011-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <urcu/config.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define FUTEX_WAIT             0
+#define FUTEX_WAKE             1
+
+/*
+ * sys_futex compatibility header.
+ * Use *only* *either of* futex_noasync OR futex_async on a given address.
+ *
+ * futex_noasync cannot be executed in signal handlers, but ensures that
+ * it will be put in a wait queue even in compatibility mode.
+ *
+ * futex_async is signal-handler safe for the wakeup. It uses polling
+ * on the wait-side in compatibility mode.
+ *
+ * BEWARE: sys_futex() FUTEX_WAIT may return early if interrupted
+ * (returns EINTR).
+ */
+
+extern int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
+               const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
+extern int compat_futex_async(int32_t *uaddr, int op, int32_t val,
+               const struct timespec *timeout, int32_t *uaddr2, int32_t val3);
+
+#ifdef CONFIG_RCU_HAVE_FUTEX
+
+#include <unistd.h>
+#include <errno.h>
+#include <urcu/compiler.h>
+#include <urcu/arch.h>
+
+static inline int futex(int32_t *uaddr, int op, int32_t val,
+               const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
+{
+       return syscall(__NR_futex, uaddr, op, val, timeout,
+                       uaddr2, val3);
+}
+
+static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
+               const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
+{
+       int ret;
+
+       ret = futex(uaddr, op, val, timeout, uaddr2, val3);
+       if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
+               /*
+                * The fallback on ENOSYS is the async-safe version of
+                * the compat futex implementation, because the
+                * async-safe compat implementation allows being used
+                * concurrently with calls to futex(). Indeed, sys_futex
+                * FUTEX_WAIT, on some architectures (mips and parisc),
+                * within a given process, spuriously return ENOSYS due
+                * to signal restart bugs on some kernel versions.
+                */
+               return compat_futex_async(uaddr, op, val, timeout,
+                               uaddr2, val3);
+       }
+       return ret;
+
+}
+
+static inline int futex_async(int32_t *uaddr, int op, int32_t val,
+               const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
+{
+       int ret;
+
+       ret = futex(uaddr, op, val, timeout, uaddr2, val3);
+       if (caa_unlikely(ret < 0 && errno == ENOSYS)) {
+               return compat_futex_async(uaddr, op, val, timeout,
+                               uaddr2, val3);
+       }
+       return ret;
+}
+
+#else
+
+static inline int futex_noasync(int32_t *uaddr, int op, int32_t val,
+               const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
+{
+       return compat_futex_noasync(uaddr, op, val, timeout, uaddr2, val3);
+}
+
+static inline int futex_async(int32_t *uaddr, int op, int32_t val,
+               const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
+{
+       return compat_futex_async(uaddr, op, val, timeout, uaddr2, val3);
+}
+
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _URCU_FUTEX_H */