* Copyright (2004) Linus Torvalds
*
* Author: Zwane Mwaikambo <zwane@fsmlabs.com>
+ *
+ * Copyright (2004) Ingo Molnar
*/
#include <linux/config.h>
#include <linux/interrupt.h>
#include <linux/module.h>
+/*
+ * Generic declaration of the raw read_trylock() function,
+ * architectures are supposed to optimize this:
+ */
+int __lockfunc generic_raw_read_trylock(rwlock_t *lock)
+{
+ _raw_read_lock(lock);
+ return 1;
+}
+EXPORT_SYMBOL(generic_raw_read_trylock);
+
int __lockfunc _spin_trylock(spinlock_t *lock)
{
preempt_disable();
}
EXPORT_SYMBOL(_spin_trylock);
-int __lockfunc _write_trylock(rwlock_t *lock)
+int __lockfunc _read_trylock(rwlock_t *lock)
{
preempt_disable();
- if (_raw_write_trylock(lock))
+ if (_raw_read_trylock(lock))
return 1;
preempt_enable();
return 0;
}
-EXPORT_SYMBOL(_write_trylock);
-
-#ifdef CONFIG_PREEMPT
-/*
- * This could be a long-held lock. If another CPU holds it for a long time,
- * and that CPU is not asked to reschedule then *this* CPU will spin on the
- * lock for a long time, even if *this* CPU is asked to reschedule.
- *
- * So what we do here, in the slow (contended) path is to spin on the lock by
- * hand while permitting preemption.
- *
- * Called inside preempt_disable().
- */
-static inline void __preempt_spin_lock(spinlock_t *lock)
-{
- if (preempt_count() > 1) {
- _raw_spin_lock(lock);
- return;
- }
-
- do {
- preempt_enable();
- while (spin_is_locked(lock))
- cpu_relax();
- preempt_disable();
- } while (!_raw_spin_trylock(lock));
-}
+EXPORT_SYMBOL(_read_trylock);
-void __lockfunc _spin_lock(spinlock_t *lock)
+int __lockfunc _write_trylock(rwlock_t *lock)
{
preempt_disable();
- if (unlikely(!_raw_spin_trylock(lock)))
- __preempt_spin_lock(lock);
-}
-
-static inline void __preempt_write_lock(rwlock_t *lock)
-{
- if (preempt_count() > 1) {
- _raw_write_lock(lock);
- return;
- }
-
- do {
- preempt_enable();
- while (rwlock_is_locked(lock))
- cpu_relax();
- preempt_disable();
- } while (!_raw_write_trylock(lock));
-}
+ if (_raw_write_trylock(lock))
+ return 1;
-void __lockfunc _write_lock(rwlock_t *lock)
-{
- preempt_disable();
- if (unlikely(!_raw_write_trylock(lock)))
- __preempt_write_lock(lock);
-}
-#else
-void __lockfunc _spin_lock(spinlock_t *lock)
-{
- preempt_disable();
- _raw_spin_lock(lock);
+ preempt_enable();
+ return 0;
}
+EXPORT_SYMBOL(_write_trylock);
-void __lockfunc _write_lock(rwlock_t *lock)
-{
- preempt_disable();
- _raw_write_lock(lock);
-}
-#endif
-EXPORT_SYMBOL(_spin_lock);
-EXPORT_SYMBOL(_write_lock);
+#ifndef CONFIG_PREEMPT
void __lockfunc _read_lock(rwlock_t *lock)
{
}
EXPORT_SYMBOL(_read_lock);
-void __lockfunc _spin_unlock(spinlock_t *lock)
-{
- _raw_spin_unlock(lock);
- preempt_enable();
-}
-EXPORT_SYMBOL(_spin_unlock);
-
-void __lockfunc _write_unlock(rwlock_t *lock)
-{
- _raw_write_unlock(lock);
- preempt_enable();
-}
-EXPORT_SYMBOL(_write_unlock);
-
-void __lockfunc _read_unlock(rwlock_t *lock)
-{
- _raw_read_unlock(lock);
- preempt_enable();
-}
-EXPORT_SYMBOL(_read_unlock);
-
unsigned long __lockfunc _spin_lock_irqsave(spinlock_t *lock)
{
unsigned long flags;
}
EXPORT_SYMBOL(_write_lock_bh);
+void __lockfunc _spin_lock(spinlock_t *lock)
+{
+ preempt_disable();
+ _raw_spin_lock(lock);
+}
+
+EXPORT_SYMBOL(_spin_lock);
+
+void __lockfunc _write_lock(rwlock_t *lock)
+{
+ preempt_disable();
+ _raw_write_lock(lock);
+}
+
+EXPORT_SYMBOL(_write_lock);
+
+#else /* CONFIG_PREEMPT: */
+
+/*
+ * This could be a long-held lock. We both prepare to spin for a long
+ * time (making _this_ CPU preemptable if possible), and we also signal
+ * towards that other CPU that it should break the lock ASAP.
+ *
+ * (We do this in a function because inlining it would be excessive.)
+ */
+
+#define BUILD_LOCK_OPS(op, locktype) \
+void __lockfunc _##op##_lock(locktype##_t *lock) \
+{ \
+ preempt_disable(); \
+ for (;;) { \
+ if (likely(_raw_##op##_trylock(lock))) \
+ break; \
+ preempt_enable(); \
+ if (!(lock)->break_lock) \
+ (lock)->break_lock = 1; \
+ while (!op##_can_lock(lock) && (lock)->break_lock) \
+ cpu_relax(); \
+ preempt_disable(); \
+ } \
+} \
+ \
+EXPORT_SYMBOL(_##op##_lock); \
+ \
+unsigned long __lockfunc _##op##_lock_irqsave(locktype##_t *lock) \
+{ \
+ unsigned long flags; \
+ \
+ preempt_disable(); \
+ for (;;) { \
+ local_irq_save(flags); \
+ if (likely(_raw_##op##_trylock(lock))) \
+ break; \
+ local_irq_restore(flags); \
+ \
+ preempt_enable(); \
+ if (!(lock)->break_lock) \
+ (lock)->break_lock = 1; \
+ while (!op##_can_lock(lock) && (lock)->break_lock) \
+ cpu_relax(); \
+ preempt_disable(); \
+ } \
+ return flags; \
+} \
+ \
+EXPORT_SYMBOL(_##op##_lock_irqsave); \
+ \
+void __lockfunc _##op##_lock_irq(locktype##_t *lock) \
+{ \
+ _##op##_lock_irqsave(lock); \
+} \
+ \
+EXPORT_SYMBOL(_##op##_lock_irq); \
+ \
+void __lockfunc _##op##_lock_bh(locktype##_t *lock) \
+{ \
+ unsigned long flags; \
+ \
+ /* */ \
+ /* Careful: we must exclude softirqs too, hence the */ \
+ /* irq-disabling. We use the generic preemption-aware */ \
+ /* function: */ \
+ /**/ \
+ flags = _##op##_lock_irqsave(lock); \
+ local_bh_disable(); \
+ local_irq_restore(flags); \
+} \
+ \
+EXPORT_SYMBOL(_##op##_lock_bh)
+
+/*
+ * Build preemption-friendly versions of the following
+ * lock-spinning functions:
+ *
+ * _[spin|read|write]_lock()
+ * _[spin|read|write]_lock_irq()
+ * _[spin|read|write]_lock_irqsave()
+ * _[spin|read|write]_lock_bh()
+ */
+BUILD_LOCK_OPS(spin, spinlock);
+BUILD_LOCK_OPS(read, rwlock);
+BUILD_LOCK_OPS(write, rwlock);
+
+#endif /* CONFIG_PREEMPT */
+
+void __lockfunc _spin_unlock(spinlock_t *lock)
+{
+ _raw_spin_unlock(lock);
+ preempt_enable();
+}
+EXPORT_SYMBOL(_spin_unlock);
+
+void __lockfunc _write_unlock(rwlock_t *lock)
+{
+ _raw_write_unlock(lock);
+ preempt_enable();
+}
+EXPORT_SYMBOL(_write_unlock);
+
+void __lockfunc _read_unlock(rwlock_t *lock)
+{
+ _raw_read_unlock(lock);
+ preempt_enable();
+}
+EXPORT_SYMBOL(_read_unlock);
+
void __lockfunc _spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
{
_raw_spin_unlock(lock);
git://git.onelab.eu / linux-2.6.git / blobdiff