The pthread APIs don't have proxies APIs, so I have to
reinvent the wheel.
Signed-off-by: Lai Jiangshan <[email protected]>
---
urcu.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++
urcu/futex.h | 2 +
urcu/static/urcu.h | 5 +++
3 files changed, 89 insertions(+), 0 deletions(-)
diff --git a/urcu.c b/urcu.c
index 064a155..bd54467 100644
--- a/urcu.c
+++ b/urcu.c
@@ -337,6 +337,88 @@ out:
}
#else /* #ifndef URCU_WAIT_READER */
+static inline void urcu_sync_proxy_lock(int32_t *lock, int32_t proxy_owner)
+{
+ assert(_CMM_LOAD_SHARED(*lock) == 0);
+ _CMM_STORE_SHARED(*lock, proxy_owner);
+}
+
+static inline void urcu_sync_proxy_unlock(int32_t *lock)
+{
+ _CMM_STORE_SHARED(*lock, 0);
+}
+
+static void urcu_sync_lock(int32_t *lock, int32_t self)
+{
+ for (;;) {
+ int32_t o = _CMM_LOAD_SHARED(*lock);
+
+ if (likely(o == 0)) {
+ o = uatomic_cmpxchg(lock, 0, self);
+ if (likely(o == 0))
+ return;
+ }
+
+ if ((o & FUTEX_WAITERS) == 0) {
+ if (uatomic_cmpxchg(lock, o, o | FUTEX_WAITERS) != o)
+ continue;
+ }
+
+ futex_async(lock, FUTEX_WAIT, o | FUTEX_WAITERS, NULL, NULL, 0);
+ }
+}
+
+/*
+ * returns:
+ * -2: error, lock is held by other.
+ * -1: error, lock is not held by anyone.
+ * 0: success unlock.
+ * 1: failed to unlock when have waiters.
+ */
+static int urcu_sync_try_unlock(int32_t *lock, int32_t self)
+{
+ int32_t o = _CMM_LOAD_SHARED(*lock);
+
+ if (likely(o == self)) {
+ o = uatomic_cmpxchg(lock, self, 0);
+ if (likely(o == self))
+ return 0;
+ }
+
+ if (o == (self | FUTEX_WAITERS))
+ return 1;
+ if (!o)
+ return -1;
+ else
+ return -2;
+}
+
+static void urcu_sync_slow_unlock(int32_t *lock)
+{
+ _CMM_STORE_SHARED(*lock, 0);
+ futex_async(lock, FUTEX_WAKE, 1, NULL, NULL, 0);
+}
+
+static void urcu_sync_unlock(int32_t *lock, int32_t self)
+{
+ int ret = urcu_sync_try_unlock(lock, self);
+
+ assert(ret == 0 || ret == 1);
+
+ if (unlikely(ret == 1))
+ urcu_sync_slow_unlock(lock);
+}
+
+static void urcu_sync_unlock_if_not_proxy_unlocked(int32_t *lock, int32_t self)
+{
+ int ret = urcu_sync_try_unlock(lock, self);
+
+ assert(ret == -1 || ret == 0 || ret == 1);
+
+ if (unlikely(ret == 1))
+ urcu_sync_slow_unlock(lock);
+}
+
#endif /* #else #ifndef URCU_WAIT_READER */
/*
diff --git a/urcu/futex.h b/urcu/futex.h
index 98acc12..e47c307 100644
--- a/urcu/futex.h
+++ b/urcu/futex.h
@@ -31,6 +31,8 @@ extern "C" {
#define FUTEX_WAIT 0
#define FUTEX_WAKE 1
+#define FUTEX_WAITERS 0x80000000
+
/*
* sys_futex compatibility header.
* Use *only* *either of* futex_noasync OR futex_async on a given address.
diff --git a/urcu/static/urcu.h b/urcu/static/urcu.h
index ebdefbe..32d1af8 100644
--- a/urcu/static/urcu.h
+++ b/urcu/static/urcu.h
@@ -308,6 +308,11 @@ static inline void _rcu_read_unlock(void)
}
#else /* #ifndef URCU_WAIT_READER */
+static inline int32_t urcu_sync_lock_onwer(int32_t *lock)
+{
+ return _CMM_LOAD_SHARED(*lock) & ~FUTEX_WAITERS;
+}
+
#endif /* #else #ifndef URCU_WAIT_READER */
#ifdef __cplusplus
--
1.7.4.4
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