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-rw-r--r--include/asm-generic/qrwlock.h130
1 files changed, 130 insertions, 0 deletions
diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
new file mode 100644
index 000000000..3aefde23d
--- /dev/null
+++ b/include/asm-generic/qrwlock.h
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Queue read/write lock
+ *
+ * (C) Copyright 2013-2014 Hewlett-Packard Development Company, L.P.
+ *
+ * Authors: Waiman Long <waiman.long@hp.com>
+ */
+#ifndef __ASM_GENERIC_QRWLOCK_H
+#define __ASM_GENERIC_QRWLOCK_H
+
+#include <linux/atomic.h>
+#include <asm/barrier.h>
+#include <asm/processor.h>
+
+#include <asm-generic/qrwlock_types.h>
+
+/*
+ * Writer states & reader shift and bias.
+ */
+#define _QW_WAITING 0x100 /* A writer is waiting */
+#define _QW_LOCKED 0x0ff /* A writer holds the lock */
+#define _QW_WMASK 0x1ff /* Writer mask */
+#define _QR_SHIFT 9 /* Reader count shift */
+#define _QR_BIAS (1U << _QR_SHIFT)
+
+/*
+ * External function declarations
+ */
+extern void queued_read_lock_slowpath(struct qrwlock *lock);
+extern void queued_write_lock_slowpath(struct qrwlock *lock);
+
+/**
+ * queued_read_trylock - try to acquire read lock of a queue rwlock
+ * @lock : Pointer to queue rwlock structure
+ * Return: 1 if lock acquired, 0 if failed
+ */
+static inline int queued_read_trylock(struct qrwlock *lock)
+{
+ u32 cnts;
+
+ cnts = atomic_read(&lock->cnts);
+ if (likely(!(cnts & _QW_WMASK))) {
+ cnts = (u32)atomic_add_return_acquire(_QR_BIAS, &lock->cnts);
+ if (likely(!(cnts & _QW_WMASK)))
+ return 1;
+ atomic_sub(_QR_BIAS, &lock->cnts);
+ }
+ return 0;
+}
+
+/**
+ * queued_write_trylock - try to acquire write lock of a queue rwlock
+ * @lock : Pointer to queue rwlock structure
+ * Return: 1 if lock acquired, 0 if failed
+ */
+static inline int queued_write_trylock(struct qrwlock *lock)
+{
+ u32 cnts;
+
+ cnts = atomic_read(&lock->cnts);
+ if (unlikely(cnts))
+ return 0;
+
+ return likely(atomic_try_cmpxchg_acquire(&lock->cnts, &cnts,
+ _QW_LOCKED));
+}
+/**
+ * queued_read_lock - acquire read lock of a queue rwlock
+ * @lock: Pointer to queue rwlock structure
+ */
+static inline void queued_read_lock(struct qrwlock *lock)
+{
+ u32 cnts;
+
+ cnts = atomic_add_return_acquire(_QR_BIAS, &lock->cnts);
+ if (likely(!(cnts & _QW_WMASK)))
+ return;
+
+ /* The slowpath will decrement the reader count, if necessary. */
+ queued_read_lock_slowpath(lock);
+}
+
+/**
+ * queued_write_lock - acquire write lock of a queue rwlock
+ * @lock : Pointer to queue rwlock structure
+ */
+static inline void queued_write_lock(struct qrwlock *lock)
+{
+ u32 cnts = 0;
+ /* Optimize for the unfair lock case where the fair flag is 0. */
+ if (likely(atomic_try_cmpxchg_acquire(&lock->cnts, &cnts, _QW_LOCKED)))
+ return;
+
+ queued_write_lock_slowpath(lock);
+}
+
+/**
+ * queued_read_unlock - release read lock of a queue rwlock
+ * @lock : Pointer to queue rwlock structure
+ */
+static inline void queued_read_unlock(struct qrwlock *lock)
+{
+ /*
+ * Atomically decrement the reader count
+ */
+ (void)atomic_sub_return_release(_QR_BIAS, &lock->cnts);
+}
+
+/**
+ * queued_write_unlock - release write lock of a queue rwlock
+ * @lock : Pointer to queue rwlock structure
+ */
+static inline void queued_write_unlock(struct qrwlock *lock)
+{
+ smp_store_release(&lock->wlocked, 0);
+}
+
+/*
+ * Remapping rwlock architecture specific functions to the corresponding
+ * queue rwlock functions.
+ */
+#define arch_read_lock(l) queued_read_lock(l)
+#define arch_write_lock(l) queued_write_lock(l)
+#define arch_read_trylock(l) queued_read_trylock(l)
+#define arch_write_trylock(l) queued_write_trylock(l)
+#define arch_read_unlock(l) queued_read_unlock(l)
+#define arch_write_unlock(l) queued_write_unlock(l)
+
+#endif /* __ASM_GENERIC_QRWLOCK_H */