Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 169 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..8a63515f0
--- /dev/null
+++ b/arch/parisc/include/asm/spinlock.h
@@ -0,0 +1,169 @@
+/* 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 *a == 0;
+}
+
+#define arch_spin_lock(lock) arch_spin_lock_flags(lock, 0)
+
+static inline void arch_spin_lock_flags(arch_spinlock_t *x,
+					 unsigned long flags)
+{
+	volatile unsigned int *a;
+
+	a = __ldcw_align(x);
+	while (__ldcw(a) == 0)
+		while (*a == 0)
+			if (flags & PSW_SM_I) {
+				local_irq_enable();
+				cpu_relax();
+				local_irq_disable();
+			} else
+				cpu_relax();
+}
+#define arch_spin_lock_flags arch_spin_lock_flags
+
+static inline void arch_spin_unlock(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+
+	a = __ldcw_align(x);
+	mb();
+	*a = 1;
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *x)
+{
+	volatile unsigned int *a;
+	int ret;
+
+	a = __ldcw_align(x);
+        ret = __ldcw(a) != 0;
+
+	return ret;
+}
+
+/*
+ * Read-write spinlocks, allowing multiple readers but only one writer.
+ * Linux rwlocks are unfair to writers; they can be starved for an indefinite
+ * time by readers.  With care, they can also be taken in interrupt context.
+ *
+ * In the PA-RISC implementation, we have a spinlock and a counter.
+ * Readers use the lock to serialise their access to the counter (which
+ * records how many readers currently hold the lock).
+ * Writers hold the spinlock, preventing any readers or other writers from
+ * grabbing the rwlock.
+ */
+
+/* Note that we have to ensure interrupts are disabled in case we're
+ * interrupted by some other code that wants to grab the same read lock */
+static  __inline__ void arch_read_lock(arch_rwlock_t *rw)
+{
+	unsigned long flags;
+	local_irq_save(flags);
+	arch_spin_lock_flags(&rw->lock, flags);
+	rw->counter++;
+	arch_spin_unlock(&rw->lock);
+	local_irq_restore(flags);
+}
+
+/* Note that we have to ensure interrupts are disabled in case we're
+ * interrupted by some other code that wants to grab the same read lock */
+static  __inline__ void arch_read_unlock(arch_rwlock_t *rw)
+{
+	unsigned long flags;
+	local_irq_save(flags);
+	arch_spin_lock_flags(&rw->lock, flags);
+	rw->counter--;
+	arch_spin_unlock(&rw->lock);
+	local_irq_restore(flags);
+}
+
+/* Note that we have to ensure interrupts are disabled in case we're
+ * interrupted by some other code that wants to grab the same read lock */
+static __inline__ int arch_read_trylock(arch_rwlock_t *rw)
+{
+	unsigned long flags;
+ retry:
+	local_irq_save(flags);
+	if (arch_spin_trylock(&rw->lock)) {
+		rw->counter++;
+		arch_spin_unlock(&rw->lock);
+		local_irq_restore(flags);
+		return 1;
+	}
+
+	local_irq_restore(flags);
+	/* If write-locked, we fail to acquire the lock */
+	if (rw->counter < 0)
+		return 0;
+
+	/* Wait until we have a realistic chance at the lock */
+	while (arch_spin_is_locked(&rw->lock) && rw->counter >= 0)
+		cpu_relax();
+
+	goto retry;
+}
+
+/* Note that we have to ensure interrupts are disabled in case we're
+ * interrupted by some other code that wants to read_trylock() this lock */
+static __inline__ void arch_write_lock(arch_rwlock_t *rw)
+{
+	unsigned long flags;
+retry:
+	local_irq_save(flags);
+	arch_spin_lock_flags(&rw->lock, flags);
+
+	if (rw->counter != 0) {
+		arch_spin_unlock(&rw->lock);
+		local_irq_restore(flags);
+
+		while (rw->counter != 0)
+			cpu_relax();
+
+		goto retry;
+	}
+
+	rw->counter = -1; /* mark as write-locked */
+	mb();
+	local_irq_restore(flags);
+}
+
+static __inline__ void arch_write_unlock(arch_rwlock_t *rw)
+{
+	rw->counter = 0;
+	arch_spin_unlock(&rw->lock);
+}
+
+/* Note that we have to ensure interrupts are disabled in case we're
+ * interrupted by some other code that wants to read_trylock() this lock */
+static __inline__ int arch_write_trylock(arch_rwlock_t *rw)
+{
+	unsigned long flags;
+	int result = 0;
+
+	local_irq_save(flags);
+	if (arch_spin_trylock(&rw->lock)) {
+		if (rw->counter == 0) {
+			rw->counter = -1;
+			result = 1;
+		} else {
+			/* Read-locked.  Oh well. */
+			arch_spin_unlock(&rw->lock);
+		}
+	}
+	local_irq_restore(flags);
+
+	return result;
+}
+
+#endif /* __ASM_SPINLOCK_H */