100 lines
2.2 KiB
C
100 lines
2.2 KiB
C
#ifndef __LINUX_BIT_SPINLOCK_H
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#define __LINUX_BIT_SPINLOCK_H
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#include <linux/kernel.h>
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#include <linux/preempt.h>
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#include <linux/atomic.h>
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/*
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* bit-based spin_lock()
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*
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* Don't use this unless you really need to: spin_lock() and spin_unlock()
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* are significantly faster.
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*/
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static inline void bit_spin_lock(int bitnum, unsigned long *addr)
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{
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/*
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* Assuming the lock is uncontended, this never enters
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* the body of the outer loop. If it is contended, then
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* within the inner loop a non-atomic test is used to
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* busywait with less bus contention for a good time to
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* attempt to acquire the lock bit.
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*/
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preempt_disable();
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
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preempt_enable();
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do {
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cpu_relax();
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} while (test_bit(bitnum, addr));
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preempt_disable();
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}
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#endif
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__acquire(bitlock);
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}
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/*
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* Return true if it was acquired
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*/
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static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
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{
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preempt_disable();
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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if (unlikely(test_and_set_bit_lock(bitnum, addr))) {
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preempt_enable();
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return 0;
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}
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#endif
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__acquire(bitlock);
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return 1;
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}
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/*
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* bit-based spin_unlock()
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*/
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static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
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{
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#ifdef CONFIG_DEBUG_SPINLOCK
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BUG_ON(!test_bit(bitnum, addr));
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#endif
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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clear_bit_unlock(bitnum, addr);
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#endif
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preempt_enable();
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__release(bitlock);
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}
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/*
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* bit-based spin_unlock()
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* non-atomic version, which can be used eg. if the bit lock itself is
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* protecting the rest of the flags in the word.
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*/
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static inline void __bit_spin_unlock(int bitnum, unsigned long *addr)
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{
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#ifdef CONFIG_DEBUG_SPINLOCK
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BUG_ON(!test_bit(bitnum, addr));
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#endif
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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__clear_bit_unlock(bitnum, addr);
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#endif
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preempt_enable();
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__release(bitlock);
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}
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/*
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* Return true if the lock is held.
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*/
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static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
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{
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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return test_bit(bitnum, addr);
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#elif defined CONFIG_PREEMPT_COUNT
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return preempt_count();
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#else
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return 1;
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#endif
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}
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#endif /* __LINUX_BIT_SPINLOCK_H */
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