1 files changed, 161 insertions, 0 deletions
diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h
new file mode 100644
index 0000000000..0b326e5225
--- /dev/null
+++ b/arch/parisc/include/asm/spinlock.h
@@ -0,0 +1,161 @@
+/* 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 void arch_spin_val_check(int lock_val)
+{
+	if (IS_ENABLED(CONFIG_LIGHTWEIGHT_SPINLOCK_CHECK))
+		asm volatile(	"andcm,= %0,%1,%%r0\n"
+				".word %2\n"
+		: : "r" (lock_val), "r" (__ARCH_SPIN_LOCK_UNLOCKED_VAL),
+			"i" (SPINLOCK_BREAK_INSN));
+}
+
+static inline int arch_spin_is_locked(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+	int lock_val;
+
+	a = __ldcw_align(x);
+	lock_val = READ_ONCE(*a);
+	arch_spin_val_check(lock_val);
+	return (lock_val == 0);
+}
+
+static inline void arch_spin_lock(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+
+	a = __ldcw_align(x);
+	do {
+		int lock_val_old;
+
+		lock_val_old = __ldcw(a);
+		arch_spin_val_check(lock_val_old);
+		if (lock_val_old)
+			return;	/* got lock */
+
+		/* wait until we should try to get lock again */
+		while (*a == 0)
+			continue;
+	} while (1);
+}
+
+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"(__ARCH_SPIN_LOCK_UNLOCKED_VAL), "r"(a) : "memory");
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+	int lock_val;
+
+	a = __ldcw_align(x);
+	lock_val = __ldcw(a);
+	arch_spin_val_check(lock_val);
+	return lock_val != 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 */