Move c_src dirs back to toplevel

[bcachefs-tools-debian] / libbcachefs / two_state_shared_lock.h

diff --git a/libbcachefs/two_state_shared_lock.h b/libbcachefs/two_state_shared_lock.h
new file mode 100644 (file)
index 0000000..9058017
--- /dev/null
+++ b/libbcachefs/two_state_shared_lock.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BCACHEFS_TWO_STATE_LOCK_H
+#define _BCACHEFS_TWO_STATE_LOCK_H
+
+#include <linux/atomic.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+
+#include "util.h"
+
+/*
+ * Two-state lock - can be taken for add or block - both states are shared,
+ * like read side of rwsem, but conflict with other state:
+ */
+typedef struct {
+       atomic_long_t           v;
+       wait_queue_head_t       wait;
+} two_state_lock_t;
+
+static inline void two_state_lock_init(two_state_lock_t *lock)
+{
+       atomic_long_set(&lock->v, 0);
+       init_waitqueue_head(&lock->wait);
+}
+
+static inline void bch2_two_state_unlock(two_state_lock_t *lock, int s)
+{
+       long i = s ? 1 : -1;
+
+       EBUG_ON(atomic_long_read(&lock->v) == 0);
+
+       if (atomic_long_sub_return_release(i, &lock->v) == 0)
+               wake_up_all(&lock->wait);
+}
+
+static inline bool bch2_two_state_trylock(two_state_lock_t *lock, int s)
+{
+       long i = s ? 1 : -1;
+       long v = atomic_long_read(&lock->v), old;
+
+       do {
+               old = v;
+
+               if (i > 0 ? v < 0 : v > 0)
+                       return false;
+       } while ((v = atomic_long_cmpxchg_acquire(&lock->v,
+                                       old, old + i)) != old);
+       return true;
+}
+
+void __bch2_two_state_lock(two_state_lock_t *, int);
+
+static inline void bch2_two_state_lock(two_state_lock_t *lock, int s)
+{
+       if (!bch2_two_state_trylock(lock, s))
+               __bch2_two_state_lock(lock, s);
+}
+
+#endif /* _BCACHEFS_TWO_STATE_LOCK_H */