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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_BIT_SPINLOCK_H
#define __LINUX_BIT_SPINLOCK_H
#include <linux/kernel.h>
#include <linux/preempt.h>
#include <linux/atomic.h>
#include <linux/bug.h>
#include <asm/processor.h> /* for cpu_relax() */
/*
* For static context analysis, we need a unique token for each possible bit
* that can be used as a bit_spinlock. The easiest way to do that is to create a
* fake context that we can cast to with the __bitlock(bitnum, addr) macro
* below, which will give us unique instances for each (bit, addr) pair that the
* static analysis can use.
*/
context_lock_struct(__context_bitlock) { };
#define __bitlock(bitnum, addr) (struct __context_bitlock *)(bitnum + (addr))
/*
* bit-based spin_lock()
*
* Don't use this unless you really need to: spin_lock() and spin_unlock()
* are significantly faster.
*/
static __always_inline void bit_spin_lock(int bitnum, unsigned long *addr)
__acquires(__bitlock(bitnum, 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 (unlikely(test_and_set_bit_lock(bitnum, addr))) {
preempt_enable();
do {
cpu_relax();
} while (test_bit(bitnum, addr));
preempt_disable();
}
#endif
__acquire(__bitlock(bitnum, addr));
}
/*
* Return true if it was acquired
*/
static __always_inline int bit_spin_trylock(int bitnum, unsigned long *addr)
__cond_acquires(true, __bitlock(bitnum, addr))
{
preempt_disable();
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
if (unlikely(test_and_set_bit_lock(bitnum, addr))) {
preempt_enable();
return 0;
}
#endif
__acquire(__bitlock(bitnum, addr));
return 1;
}
/*
* bit-based spin_unlock()
*/
static __always_inline void bit_spin_unlock(int bitnum, unsigned long *addr)
__releases(__bitlock(bitnum, addr))
{
#ifdef CONFIG_DEBUG_SPINLOCK
BUG_ON(!test_bit(bitnum, addr));
#endif
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
clear_bit_unlock(bitnum, addr);
#endif
preempt_enable();
__release(__bitlock(bitnum, addr));
}
/*
* bit-based spin_unlock()
* non-atomic version, which can be used eg. if the bit lock itself is
* protecting the rest of the flags in the word.
*/
static __always_inline void __bit_spin_unlock(int bitnum, unsigned long *addr)
__releases(__bitlock(bitnum, addr))
{
#ifdef CONFIG_DEBUG_SPINLOCK
BUG_ON(!test_bit(bitnum, addr));
#endif
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
__clear_bit_unlock(bitnum, addr);
#endif
preempt_enable();
__release(__bitlock(bitnum, addr));
}
/*
* 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_COUNT
return preempt_count();
#else
return 1;
#endif
}
#endif /* __LINUX_BIT_SPINLOCK_H */
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