102 lines · c
1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef __LINUX_BIT_SPINLOCK_H3#define __LINUX_BIT_SPINLOCK_H4 5#include <linux/kernel.h>6#include <linux/preempt.h>7#include <linux/atomic.h>8#include <linux/bug.h>9 10/*11 * bit-based spin_lock()12 *13 * Don't use this unless you really need to: spin_lock() and spin_unlock()14 * are significantly faster.15 */16static inline void bit_spin_lock(int bitnum, unsigned long *addr)17{18 /*19 * Assuming the lock is uncontended, this never enters20 * the body of the outer loop. If it is contended, then21 * within the inner loop a non-atomic test is used to22 * busywait with less bus contention for a good time to23 * attempt to acquire the lock bit.24 */25 preempt_disable();26#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)27 while (unlikely(test_and_set_bit_lock(bitnum, addr))) {28 preempt_enable();29 do {30 cpu_relax();31 } while (test_bit(bitnum, addr));32 preempt_disable();33 }34#endif35 __acquire(bitlock);36}37 38/*39 * Return true if it was acquired40 */41static inline int bit_spin_trylock(int bitnum, unsigned long *addr)42{43 preempt_disable();44#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)45 if (unlikely(test_and_set_bit_lock(bitnum, addr))) {46 preempt_enable();47 return 0;48 }49#endif50 __acquire(bitlock);51 return 1;52}53 54/*55 * bit-based spin_unlock()56 */57static inline void bit_spin_unlock(int bitnum, unsigned long *addr)58{59#ifdef CONFIG_DEBUG_SPINLOCK60 BUG_ON(!test_bit(bitnum, addr));61#endif62#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)63 clear_bit_unlock(bitnum, addr);64#endif65 preempt_enable();66 __release(bitlock);67}68 69/*70 * bit-based spin_unlock()71 * non-atomic version, which can be used eg. if the bit lock itself is72 * protecting the rest of the flags in the word.73 */74static inline void __bit_spin_unlock(int bitnum, unsigned long *addr)75{76#ifdef CONFIG_DEBUG_SPINLOCK77 BUG_ON(!test_bit(bitnum, addr));78#endif79#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)80 __clear_bit_unlock(bitnum, addr);81#endif82 preempt_enable();83 __release(bitlock);84}85 86/*87 * Return true if the lock is held.88 */89static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)90{91#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)92 return test_bit(bitnum, addr);93#elif defined CONFIG_PREEMPT_COUNT94 return preempt_count();95#else96 return 1;97#endif98}99 100#endif /* __LINUX_BIT_SPINLOCK_H */101 102