78 lines
1.7 KiB
C
78 lines
1.7 KiB
C
#ifndef __LINUX_BIT_SPINLOCK_H
|
|
#define __LINUX_BIT_SPINLOCK_H
|
|
|
|
/*
|
|
* bit-based spin_lock()
|
|
*
|
|
* Don't use this unless you really need to: spin_lock() and spin_unlock()
|
|
* are significantly faster.
|
|
*/
|
|
static inline void bit_spin_lock(int bitnum, unsigned long *addr)
|
|
{
|
|
/*
|
|
* Assuming the lock is uncontended, this never enters
|
|
* the body of the outer loop. If it is contended, then
|
|
* within the inner loop a non-atomic test is used to
|
|
* busywait with less bus contention for a good time to
|
|
* attempt to acquire the lock bit.
|
|
*/
|
|
preempt_disable();
|
|
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
|
|
while (test_and_set_bit(bitnum, addr)) {
|
|
while (test_bit(bitnum, addr)) {
|
|
preempt_enable();
|
|
cpu_relax();
|
|
preempt_disable();
|
|
}
|
|
}
|
|
#endif
|
|
__acquire(bitlock);
|
|
}
|
|
|
|
/*
|
|
* Return true if it was acquired
|
|
*/
|
|
static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
|
|
{
|
|
preempt_disable();
|
|
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
|
|
if (test_and_set_bit(bitnum, addr)) {
|
|
preempt_enable();
|
|
return 0;
|
|
}
|
|
#endif
|
|
__acquire(bitlock);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* bit-based spin_unlock()
|
|
*/
|
|
static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
|
|
{
|
|
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
|
|
BUG_ON(!test_bit(bitnum, addr));
|
|
smp_mb__before_clear_bit();
|
|
clear_bit(bitnum, addr);
|
|
#endif
|
|
preempt_enable();
|
|
__release(bitlock);
|
|
}
|
|
|
|
/*
|
|
* Return true if the lock is held.
|
|
*/
|
|
static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
|
|
{
|
|
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
|
|
return test_bit(bitnum, addr);
|
|
#elif defined CONFIG_PREEMPT
|
|
return preempt_count();
|
|
#else
|
|
return 1;
|
|
#endif
|
|
}
|
|
|
|
#endif /* __LINUX_BIT_SPINLOCK_H */
|
|
|