1 #ifndef _ASM_GENERIC_BITOPS_ATOMIC_H_
2 #define _ASM_GENERIC_BITOPS_ATOMIC_H_
3 
4 #include <asm/types.h>
5 #include <linux/irqflags.h>
6 
7 #ifdef CONFIG_SMP
8 #include <asm/spinlock.h>
9 #include <asm/cache.h>		/* we use L1_CACHE_BYTES */
10 
11 /* Use an array of spinlocks for our atomic_ts.
12  * Hash function to index into a different SPINLOCK.
13  * Since "a" is usually an address, use one spinlock per cacheline.
14  */
15 #  define ATOMIC_HASH_SIZE 4
16 #  define ATOMIC_HASH(a) (&(__atomic_hash[ (((unsigned long) a)/L1_CACHE_BYTES) & (ATOMIC_HASH_SIZE-1) ]))
17 
18 extern arch_spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] __lock_aligned;
19 
20 /* Can't use raw_spin_lock_irq because of #include problems, so
21  * this is the substitute */
22 #define _atomic_spin_lock_irqsave(l,f) do {	\
23 	arch_spinlock_t *s = ATOMIC_HASH(l);	\
24 	local_irq_save(f);			\
25 	arch_spin_lock(s);			\
26 } while(0)
27 
28 #define _atomic_spin_unlock_irqrestore(l,f) do {	\
29 	arch_spinlock_t *s = ATOMIC_HASH(l);		\
30 	arch_spin_unlock(s);				\
31 	local_irq_restore(f);				\
32 } while(0)
33 
34 
35 #else
36 #  define _atomic_spin_lock_irqsave(l,f) do { local_irq_save(f); } while (0)
37 #  define _atomic_spin_unlock_irqrestore(l,f) do { local_irq_restore(f); } while (0)
38 #endif
39 
40 /*
41  * NMI events can occur at any time, including when interrupts have been
42  * disabled by *_irqsave().  So you can get NMI events occurring while a
43  * *_bit function is holding a spin lock.  If the NMI handler also wants
44  * to do bit manipulation (and they do) then you can get a deadlock
45  * between the original caller of *_bit() and the NMI handler.
46  *
47  * by Keith Owens
48  */
49 
50 /**
51  * set_bit - Atomically set a bit in memory
52  * @nr: the bit to set
53  * @addr: the address to start counting from
54  *
55  * This function is atomic and may not be reordered.  See __set_bit()
56  * if you do not require the atomic guarantees.
57  *
58  * Note: there are no guarantees that this function will not be reordered
59  * on non x86 architectures, so if you are writing portable code,
60  * make sure not to rely on its reordering guarantees.
61  *
62  * Note that @nr may be almost arbitrarily large; this function is not
63  * restricted to acting on a single-word quantity.
64  */
65 static inline void set_bit(int nr, volatile unsigned long *addr)
66 {
67 	unsigned long mask = BIT_MASK(nr);
68 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
69 	unsigned long flags;
70 
71 	_atomic_spin_lock_irqsave(p, flags);
72 	*p  |= mask;
73 	_atomic_spin_unlock_irqrestore(p, flags);
74 }
75 
76 /**
77  * clear_bit - Clears a bit in memory
78  * @nr: Bit to clear
79  * @addr: Address to start counting from
80  *
81  * clear_bit() is atomic and may not be reordered.  However, it does
82  * not contain a memory barrier, so if it is used for locking purposes,
83  * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
84  * in order to ensure changes are visible on other processors.
85  */
86 static inline void clear_bit(int nr, volatile unsigned long *addr)
87 {
88 	unsigned long mask = BIT_MASK(nr);
89 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
90 	unsigned long flags;
91 
92 	_atomic_spin_lock_irqsave(p, flags);
93 	*p &= ~mask;
94 	_atomic_spin_unlock_irqrestore(p, flags);
95 }
96 
97 /**
98  * change_bit - Toggle a bit in memory
99  * @nr: Bit to change
100  * @addr: Address to start counting from
101  *
102  * change_bit() is atomic and may not be reordered. It may be
103  * reordered on other architectures than x86.
104  * Note that @nr may be almost arbitrarily large; this function is not
105  * restricted to acting on a single-word quantity.
106  */
107 static inline void change_bit(int nr, volatile unsigned long *addr)
108 {
109 	unsigned long mask = BIT_MASK(nr);
110 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
111 	unsigned long flags;
112 
113 	_atomic_spin_lock_irqsave(p, flags);
114 	*p ^= mask;
115 	_atomic_spin_unlock_irqrestore(p, flags);
116 }
117 
118 /**
119  * test_and_set_bit - Set a bit and return its old value
120  * @nr: Bit to set
121  * @addr: Address to count from
122  *
123  * This operation is atomic and cannot be reordered.
124  * It may be reordered on other architectures than x86.
125  * It also implies a memory barrier.
126  */
127 static inline int test_and_set_bit(int nr, volatile unsigned long *addr)
128 {
129 	unsigned long mask = BIT_MASK(nr);
130 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
131 	unsigned long old;
132 	unsigned long flags;
133 
134 	_atomic_spin_lock_irqsave(p, flags);
135 	old = *p;
136 	*p = old | mask;
137 	_atomic_spin_unlock_irqrestore(p, flags);
138 
139 	return (old & mask) != 0;
140 }
141 
142 /**
143  * test_and_clear_bit - Clear a bit and return its old value
144  * @nr: Bit to clear
145  * @addr: Address to count from
146  *
147  * This operation is atomic and cannot be reordered.
148  * It can be reorderdered on other architectures other than x86.
149  * It also implies a memory barrier.
150  */
151 static inline int test_and_clear_bit(int nr, volatile unsigned long *addr)
152 {
153 	unsigned long mask = BIT_MASK(nr);
154 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
155 	unsigned long old;
156 	unsigned long flags;
157 
158 	_atomic_spin_lock_irqsave(p, flags);
159 	old = *p;
160 	*p = old & ~mask;
161 	_atomic_spin_unlock_irqrestore(p, flags);
162 
163 	return (old & mask) != 0;
164 }
165 
166 /**
167  * test_and_change_bit - Change a bit and return its old value
168  * @nr: Bit to change
169  * @addr: Address to count from
170  *
171  * This operation is atomic and cannot be reordered.
172  * It also implies a memory barrier.
173  */
174 static inline int test_and_change_bit(int nr, volatile unsigned long *addr)
175 {
176 	unsigned long mask = BIT_MASK(nr);
177 	unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
178 	unsigned long old;
179 	unsigned long flags;
180 
181 	_atomic_spin_lock_irqsave(p, flags);
182 	old = *p;
183 	*p = old ^ mask;
184 	_atomic_spin_unlock_irqrestore(p, flags);
185 
186 	return (old & mask) != 0;
187 }
188 
189 #endif /* _ASM_GENERIC_BITOPS_ATOMIC_H */
190