| xj | b04a402 | 2021-11-25 15:01:52 +0800 | [diff] [blame] | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
| 2 | #ifndef _ASM_GENERIC_BITOPS_LOCK_H_ |
| 3 | #define _ASM_GENERIC_BITOPS_LOCK_H_ |
| 4 | |
| 5 | #include <linux/atomic.h> |
| 6 | #include <linux/compiler.h> |
| 7 | #include <asm/barrier.h> |
| 8 | |
| 9 | /** |
| 10 | * test_and_set_bit_lock - Set a bit and return its old value, for lock |
| 11 | * @nr: Bit to set |
| 12 | * @addr: Address to count from |
| 13 | * |
| 14 | * This operation is atomic and provides acquire barrier semantics if |
| 15 | * the returned value is 0. |
| 16 | * It can be used to implement bit locks. |
| 17 | */ |
| 18 | static inline int test_and_set_bit_lock(unsigned int nr, |
| 19 | volatile unsigned long *p) |
| 20 | { |
| 21 | long old; |
| 22 | unsigned long mask = BIT_MASK(nr); |
| 23 | |
| 24 | p += BIT_WORD(nr); |
| 25 | if (READ_ONCE(*p) & mask) |
| 26 | return 1; |
| 27 | |
| 28 | old = atomic_long_fetch_or_acquire(mask, (atomic_long_t *)p); |
| 29 | return !!(old & mask); |
| 30 | } |
| 31 | |
| 32 | |
| 33 | /** |
| 34 | * clear_bit_unlock - Clear a bit in memory, for unlock |
| 35 | * @nr: the bit to set |
| 36 | * @addr: the address to start counting from |
| 37 | * |
| 38 | * This operation is atomic and provides release barrier semantics. |
| 39 | */ |
| 40 | static inline void clear_bit_unlock(unsigned int nr, volatile unsigned long *p) |
| 41 | { |
| 42 | p += BIT_WORD(nr); |
| 43 | atomic_long_fetch_andnot_release(BIT_MASK(nr), (atomic_long_t *)p); |
| 44 | } |
| 45 | |
| 46 | /** |
| 47 | * __clear_bit_unlock - Clear a bit in memory, for unlock |
| 48 | * @nr: the bit to set |
| 49 | * @addr: the address to start counting from |
| 50 | * |
| 51 | * A weaker form of clear_bit_unlock() as used by __bit_lock_unlock(). If all |
| 52 | * the bits in the word are protected by this lock some archs can use weaker |
| 53 | * ops to safely unlock. |
| 54 | * |
| 55 | * See for example x86's implementation. |
| 56 | */ |
| 57 | static inline void __clear_bit_unlock(unsigned int nr, |
| 58 | volatile unsigned long *p) |
| 59 | { |
| 60 | unsigned long old; |
| 61 | |
| 62 | p += BIT_WORD(nr); |
| 63 | old = READ_ONCE(*p); |
| 64 | old &= ~BIT_MASK(nr); |
| 65 | atomic_long_set_release((atomic_long_t *)p, old); |
| 66 | } |
| 67 | |
| 68 | /** |
| 69 | * clear_bit_unlock_is_negative_byte - Clear a bit in memory and test if bottom |
| 70 | * byte is negative, for unlock. |
| 71 | * @nr: the bit to clear |
| 72 | * @addr: the address to start counting from |
| 73 | * |
| 74 | * This is a bit of a one-trick-pony for the filemap code, which clears |
| 75 | * PG_locked and tests PG_waiters, |
| 76 | */ |
| 77 | #ifndef clear_bit_unlock_is_negative_byte |
| 78 | static inline bool clear_bit_unlock_is_negative_byte(unsigned int nr, |
| 79 | volatile unsigned long *p) |
| 80 | { |
| 81 | long old; |
| 82 | unsigned long mask = BIT_MASK(nr); |
| 83 | |
| 84 | p += BIT_WORD(nr); |
| 85 | old = atomic_long_fetch_andnot_release(mask, (atomic_long_t *)p); |
| 86 | return !!(old & BIT(7)); |
| 87 | } |
| 88 | #define clear_bit_unlock_is_negative_byte clear_bit_unlock_is_negative_byte |
| 89 | #endif |
| 90 | |
| 91 | #endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */ |