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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - include/linux/bit_spinlock.h
1 #ifndef __LINUX_BIT_SPINLOCK_H
2 #define __LINUX_BIT_SPINLOCK_H
5 * bit-based spin_lock()
7 * Don't use this unless you really need to: spin_lock() and spin_unlock()
8 * are significantly faster.
10 static inline void bit_spin_lock(int bitnum
, unsigned long *addr
)
13 * Assuming the lock is uncontended, this never enters
14 * the body of the outer loop. If it is contended, then
15 * within the inner loop a non-atomic test is used to
16 * busywait with less bus contention for a good time to
17 * attempt to acquire the lock bit.
20 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
21 while (test_and_set_bit(bitnum
, addr
)) {
22 while (test_bit(bitnum
, addr
)) {
33 * Return true if it was acquired
35 static inline int bit_spin_trylock(int bitnum
, unsigned long *addr
)
38 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
39 if (test_and_set_bit(bitnum
, addr
)) {
49 * bit-based spin_unlock()
51 static inline void bit_spin_unlock(int bitnum
, unsigned long *addr
)
53 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
54 BUG_ON(!test_bit(bitnum
, addr
));
55 smp_mb__before_clear_bit();
56 clear_bit(bitnum
, addr
);
63 * Return true if the lock is held.
65 static inline int bit_spin_is_locked(int bitnum
, unsigned long *addr
)
67 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
68 return test_bit(bitnum
, addr
);
69 #elif defined CONFIG_PREEMPT
70 return preempt_count();
76 #endif /* __LINUX_BIT_SPINLOCK_H */