1 files changed, 134 insertions, 0 deletions
diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h
new file mode 100644
index 000000000..a6e5d66a7
--- /dev/null
+++ b/arch/parisc/include/asm/spinlock.h
@@ -0,0 +1,134 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_SPINLOCK_H
+#define __ASM_SPINLOCK_H
+
+#include <asm/barrier.h>
+#include <asm/ldcw.h>
+#include <asm/processor.h>
+#include <asm/spinlock_types.h>
+
+static inline int arch_spin_is_locked(arch_spinlock_t *x)
+{
+	volatile unsigned int *a = __ldcw_align(x);
+	return READ_ONCE(*a) == 0;
+}
+
+static inline void arch_spin_lock(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+
+	a = __ldcw_align(x);
+	while (__ldcw(a) == 0)
+		while (*a == 0)
+			continue;
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+
+	a = __ldcw_align(x);
+	/* Release with ordered store. */
+	__asm__ __volatile__("stw,ma %0,0(%1)" : : "r"(1), "r"(a) : "memory");
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+
+	a = __ldcw_align(x);
+	return __ldcw(a) != 0;
+}
+
+/*
+ * Read-write spinlocks, allowing multiple readers but only one writer.
+ * Unfair locking as Writers could be starved indefinitely by Reader(s)
+ *
+ * The spinlock itself is contained in @counter and access to it is
+ * serialized with @lock_mutex.
+ */
+
+/* 1 - lock taken successfully */
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	arch_spin_lock(&(rw->lock_mutex));
+
+	/*
+	 * zero means writer holds the lock exclusively, deny Reader.
+	 * Otherwise grant lock to first/subseq reader
+	 */
+	if (rw->counter > 0) {
+		rw->counter--;
+		ret = 1;
+	}
+
+	arch_spin_unlock(&(rw->lock_mutex));
+	local_irq_restore(flags);
+
+	return ret;
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	arch_spin_lock(&(rw->lock_mutex));
+
+	/*
+	 * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
+	 * deny writer. Otherwise if unlocked grant to writer
+	 * Hence the claim that Linux rwlocks are unfair to writers.
+	 * (can be starved for an indefinite time by readers).
+	 */
+	if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
+		rw->counter = 0;
+		ret = 1;
+	}
+	arch_spin_unlock(&(rw->lock_mutex));
+	local_irq_restore(flags);
+
+	return ret;
+}
+
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+	while (!arch_read_trylock(rw))
+		cpu_relax();
+}
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+	while (!arch_write_trylock(rw))
+		cpu_relax();
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	arch_spin_lock(&(rw->lock_mutex));
+	rw->counter++;
+	arch_spin_unlock(&(rw->lock_mutex));
+	local_irq_restore(flags);
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	arch_spin_lock(&(rw->lock_mutex));
+	rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
+	arch_spin_unlock(&(rw->lock_mutex));
+	local_irq_restore(flags);
+}
+
+#endif /* __ASM_SPINLOCK_H */