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authorKyle McMartin <kyle@mcmartin.ca>2008-07-28 23:02:13 -0400
committerKyle McMartin <kyle@hera.kernel.org>2008-10-10 16:32:29 +0000
commitdeae26bf6a10e47983606f5df080b91e97650ead (patch)
tree84a8a68145d0f713d7c5a1f9e6b3b03be9b3a4c8 /arch/parisc/include/asm/spinlock.h
parent6c86cb8237bf08443806089130dc108051569a93 (diff)
parisc: move include/asm-parisc to arch/parisc/include/asm
Diffstat (limited to 'arch/parisc/include/asm/spinlock.h')
-rw-r--r--arch/parisc/include/asm/spinlock.h194
1 files changed, 194 insertions, 0 deletions
diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h
new file mode 100644
index 000000000000..f3d2090a18dc
--- /dev/null
+++ b/arch/parisc/include/asm/spinlock.h
@@ -0,0 +1,194 @@
+#ifndef __ASM_SPINLOCK_H
+#define __ASM_SPINLOCK_H
+
+#include <asm/system.h>
+#include <asm/processor.h>
+#include <asm/spinlock_types.h>
+
+static inline int __raw_spin_is_locked(raw_spinlock_t *x)
+{
+ volatile unsigned int *a = __ldcw_align(x);
+ return *a == 0;
+}
+
+#define __raw_spin_lock(lock) __raw_spin_lock_flags(lock, 0)
+#define __raw_spin_unlock_wait(x) \
+ do { cpu_relax(); } while (__raw_spin_is_locked(x))
+
+static inline void __raw_spin_lock_flags(raw_spinlock_t *x,
+ unsigned long flags)
+{
+ volatile unsigned int *a;
+
+ mb();
+ 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();
+ mb();
+}
+
+static inline void __raw_spin_unlock(raw_spinlock_t *x)
+{
+ volatile unsigned int *a;
+ mb();
+ a = __ldcw_align(x);
+ *a = 1;
+ mb();
+}
+
+static inline int __raw_spin_trylock(raw_spinlock_t *x)
+{
+ volatile unsigned int *a;
+ int ret;
+
+ mb();
+ a = __ldcw_align(x);
+ ret = __ldcw(a) != 0;
+ mb();
+
+ 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 __raw_read_lock(raw_rwlock_t *rw)
+{
+ unsigned long flags;
+ local_irq_save(flags);
+ __raw_spin_lock_flags(&rw->lock, flags);
+ rw->counter++;
+ __raw_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 __raw_read_unlock(raw_rwlock_t *rw)
+{
+ unsigned long flags;
+ local_irq_save(flags);
+ __raw_spin_lock_flags(&rw->lock, flags);
+ rw->counter--;
+ __raw_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 __raw_read_trylock(raw_rwlock_t *rw)
+{
+ unsigned long flags;
+ retry:
+ local_irq_save(flags);
+ if (__raw_spin_trylock(&rw->lock)) {
+ rw->counter++;
+ __raw_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 (__raw_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 __raw_write_lock(raw_rwlock_t *rw)
+{
+ unsigned long flags;
+retry:
+ local_irq_save(flags);
+ __raw_spin_lock_flags(&rw->lock, flags);
+
+ if (rw->counter != 0) {
+ __raw_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 __raw_write_unlock(raw_rwlock_t *rw)
+{
+ rw->counter = 0;
+ __raw_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 __raw_write_trylock(raw_rwlock_t *rw)
+{
+ unsigned long flags;
+ int result = 0;
+
+ local_irq_save(flags);
+ if (__raw_spin_trylock(&rw->lock)) {
+ if (rw->counter == 0) {
+ rw->counter = -1;
+ result = 1;
+ } else {
+ /* Read-locked. Oh well. */
+ __raw_spin_unlock(&rw->lock);
+ }
+ }
+ local_irq_restore(flags);
+
+ return result;
+}
+
+/*
+ * read_can_lock - would read_trylock() succeed?
+ * @lock: the rwlock in question.
+ */
+static __inline__ int __raw_read_can_lock(raw_rwlock_t *rw)
+{
+ return rw->counter >= 0;
+}
+
+/*
+ * write_can_lock - would write_trylock() succeed?
+ * @lock: the rwlock in question.
+ */
+static __inline__ int __raw_write_can_lock(raw_rwlock_t *rw)
+{
+ return !rw->counter;
+}
+
+#define _raw_spin_relax(lock) cpu_relax()
+#define _raw_read_relax(lock) cpu_relax()
+#define _raw_write_relax(lock) cpu_relax()
+
+#endif /* __ASM_SPINLOCK_H */