blob: 5cc641c5083465ac468cb96b773954b945c02a3e (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
/*
* Pull in the generic implementation for the mutex fastpath.
*
* TODO: implement optimized primitives instead, or leave the generic
* implementation in place, or pick the atomic_xchg() based generic
* implementation. (see asm-generic/mutex-xchg.h for details)
*/
#ifndef _ASM_MUTEX_H
#define _ASM_MUTEX_H
#ifndef CONFIG_SMP
#include <asm-generic/mutex.h>
#else
static inline void
__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
{
if (unlikely(atomic_dec_return(count) < 0))
fail_fn(count);
else
smp_mb();
}
static inline int
__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
{
if (unlikely(atomic_dec_return(count) < 0))
return fail_fn(count);
else {
smp_mb();
return 0;
}
}
static inline void
__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
{
smp_mb();
if (unlikely(atomic_inc_return(count) <= 0))
fail_fn(count);
}
#define __mutex_slowpath_needs_to_unlock() 1
static inline int
__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
{
/*
* We have two variants here. The cmpxchg based one is the best one
* because it never induce a false contention state. It is included
* here because architectures using the inc/dec algorithms over the
* xchg ones are much more likely to support cmpxchg natively.
*
* If not we fall back to the spinlock based variant - that is
* just as efficient (and simpler) as a 'destructive' probing of
* the mutex state would be.
*/
#ifdef __HAVE_ARCH_CMPXCHG
if (likely(atomic_cmpxchg(count, 1, 0) == 1)) {
smp_mb();
return 1;
}
return 0;
#else
return fail_fn(count);
#endif
}
#endif
#endif
|
