diff options
author | Shaohua Li <shli@kernel.org> | 2012-10-08 19:32:18 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-09 03:22:46 -0400 |
commit | e79bee24fd6134f90af4228cfebd010136d67631 (patch) | |
tree | ecc678106bbf4672becca8f798aaf94276eaa2c4 /include/linux/atomic.h | |
parent | 435b405c06119d93333738172b8060b0ed12af41 (diff) |
atomic: implement generic atomic_dec_if_positive()
The x86 implementation of atomic_dec_if_positive is quite generic, so make
it available to all architectures.
This is needed for "swap: add a simple detector for inappropriate swapin
readahead".
[akpm@linux-foundation.org: do the "#define foo foo" trick in the conventional manner]
Signed-off-by: Shaohua Li <shli@fusionio.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/atomic.h')
-rw-r--r-- | include/linux/atomic.h | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 70cfcb2d63c4..5b08a8540ecf 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h | |||
@@ -86,6 +86,31 @@ static inline int atomic_dec_unless_positive(atomic_t *p) | |||
86 | } | 86 | } |
87 | #endif | 87 | #endif |
88 | 88 | ||
89 | /* | ||
90 | * atomic_dec_if_positive - decrement by 1 if old value positive | ||
91 | * @v: pointer of type atomic_t | ||
92 | * | ||
93 | * The function returns the old value of *v minus 1, even if | ||
94 | * the atomic variable, v, was not decremented. | ||
95 | */ | ||
96 | #ifndef atomic_dec_if_positive | ||
97 | static inline int atomic_dec_if_positive(atomic_t *v) | ||
98 | { | ||
99 | int c, old, dec; | ||
100 | c = atomic_read(v); | ||
101 | for (;;) { | ||
102 | dec = c - 1; | ||
103 | if (unlikely(dec < 0)) | ||
104 | break; | ||
105 | old = atomic_cmpxchg((v), c, dec); | ||
106 | if (likely(old == c)) | ||
107 | break; | ||
108 | c = old; | ||
109 | } | ||
110 | return dec; | ||
111 | } | ||
112 | #endif | ||
113 | |||
89 | #ifndef CONFIG_ARCH_HAS_ATOMIC_OR | 114 | #ifndef CONFIG_ARCH_HAS_ATOMIC_OR |
90 | static inline void atomic_or(int i, atomic_t *v) | 115 | static inline void atomic_or(int i, atomic_t *v) |
91 | { | 116 | { |