mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-27 03:10:12 +00:00
84c6591103
The lock bitops can be implemented more efficiently using the atomic_fetch_*() ops, which provide finer-grained control over the memory ordering semantics than the bitops. Signed-off-by: Will Deacon <will.deacon@arm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arm-kernel@lists.infradead.org Cc: yamada.masahiro@socionext.com Link: https://lore.kernel.org/lkml/1529412794-17720-8-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
91 lines
2.4 KiB
C
91 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _ASM_GENERIC_BITOPS_LOCK_H_
|
|
#define _ASM_GENERIC_BITOPS_LOCK_H_
|
|
|
|
#include <linux/atomic.h>
|
|
#include <linux/compiler.h>
|
|
#include <asm/barrier.h>
|
|
|
|
/**
|
|
* test_and_set_bit_lock - Set a bit and return its old value, for lock
|
|
* @nr: Bit to set
|
|
* @addr: Address to count from
|
|
*
|
|
* This operation is atomic and provides acquire barrier semantics if
|
|
* the returned value is 0.
|
|
* It can be used to implement bit locks.
|
|
*/
|
|
static inline int test_and_set_bit_lock(unsigned int nr,
|
|
volatile unsigned long *p)
|
|
{
|
|
long old;
|
|
unsigned long mask = BIT_MASK(nr);
|
|
|
|
p += BIT_WORD(nr);
|
|
if (READ_ONCE(*p) & mask)
|
|
return 1;
|
|
|
|
old = atomic_long_fetch_or_acquire(mask, (atomic_long_t *)p);
|
|
return !!(old & mask);
|
|
}
|
|
|
|
|
|
/**
|
|
* clear_bit_unlock - Clear a bit in memory, for unlock
|
|
* @nr: the bit to set
|
|
* @addr: the address to start counting from
|
|
*
|
|
* This operation is atomic and provides release barrier semantics.
|
|
*/
|
|
static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p)
|
|
{
|
|
p += BIT_WORD(nr);
|
|
atomic_long_fetch_andnot_release(BIT_MASK(nr), (atomic_long_t *)p);
|
|
}
|
|
|
|
/**
|
|
* __clear_bit_unlock - Clear a bit in memory, for unlock
|
|
* @nr: the bit to set
|
|
* @addr: the address to start counting from
|
|
*
|
|
* A weaker form of clear_bit_unlock() as used by __bit_lock_unlock(). If all
|
|
* the bits in the word are protected by this lock some archs can use weaker
|
|
* ops to safely unlock.
|
|
*
|
|
* See for example x86's implementation.
|
|
*/
|
|
static inline void __clear_bit_unlock(unsigned int nr,
|
|
volatile unsigned long *p)
|
|
{
|
|
unsigned long old;
|
|
|
|
p += BIT_WORD(nr);
|
|
old = READ_ONCE(*p);
|
|
old &= ~BIT_MASK(nr);
|
|
atomic_long_set_release((atomic_long_t *)p, old);
|
|
}
|
|
|
|
/**
|
|
* clear_bit_unlock_is_negative_byte - Clear a bit in memory and test if bottom
|
|
* byte is negative, for unlock.
|
|
* @nr: the bit to clear
|
|
* @addr: the address to start counting from
|
|
*
|
|
* This is a bit of a one-trick-pony for the filemap code, which clears
|
|
* PG_locked and tests PG_waiters,
|
|
*/
|
|
#ifndef clear_bit_unlock_is_negative_byte
|
|
static inline bool clear_bit_unlock_is_negative_byte(unsigned int nr,
|
|
volatile unsigned long *p)
|
|
{
|
|
long old;
|
|
unsigned long mask = BIT_MASK(nr);
|
|
|
|
p += BIT_WORD(nr);
|
|
old = atomic_long_fetch_andnot_release(mask, (atomic_long_t *)p);
|
|
return !!(old & BIT(7));
|
|
}
|
|
#define clear_bit_unlock_is_negative_byte clear_bit_unlock_is_negative_byte
|
|
#endif
|
|
|
|
#endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */
|