diff options
author | David S. Miller <davem@davemloft.net> | 2005-09-15 00:47:01 -0400 |
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committer | David S. Miller <davem@davemloft.net> | 2005-09-15 00:47:01 -0400 |
commit | 4db2ce0199f04b6e99999f22e28ef9a0ae5f0d2f (patch) | |
tree | 87a00c97e02a77cdfec517398caa3f1d8f6a2f0d /lib | |
parent | 4a805e863d6b9466baf7084e1d6fdbe6e0628d8e (diff) |
[LIB]: Consolidate _atomic_dec_and_lock()
Several implementations were essentialy a common piece of C code using
the cmpxchg() macro. Put the implementation in one spot that everyone
can share, and convert sparc64 over to using this.
Alpha is the lone arch-specific implementation, which codes up a
special fast path for the common case in order to avoid GP reloading
which a pure C version would require.
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/dec_and_lock.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c index 2377af057d09..305a9663aee3 100644 --- a/lib/dec_and_lock.c +++ b/lib/dec_and_lock.c | |||
@@ -1,7 +1,41 @@ | |||
1 | #include <linux/module.h> | 1 | #include <linux/module.h> |
2 | #include <linux/spinlock.h> | 2 | #include <linux/spinlock.h> |
3 | #include <asm/atomic.h> | 3 | #include <asm/atomic.h> |
4 | #include <asm/system.h> | ||
4 | 5 | ||
6 | #ifdef __HAVE_ARCH_CMPXCHG | ||
7 | /* | ||
8 | * This is an implementation of the notion of "decrement a | ||
9 | * reference count, and return locked if it decremented to zero". | ||
10 | * | ||
11 | * This implementation can be used on any architecture that | ||
12 | * has a cmpxchg, and where atomic->value is an int holding | ||
13 | * the value of the atomic (i.e. the high bits aren't used | ||
14 | * for a lock or anything like that). | ||
15 | */ | ||
16 | int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) | ||
17 | { | ||
18 | int counter; | ||
19 | int newcount; | ||
20 | |||
21 | for (;;) { | ||
22 | counter = atomic_read(atomic); | ||
23 | newcount = counter - 1; | ||
24 | if (!newcount) | ||
25 | break; /* do it the slow way */ | ||
26 | |||
27 | newcount = cmpxchg(&atomic->counter, counter, newcount); | ||
28 | if (newcount == counter) | ||
29 | return 0; | ||
30 | } | ||
31 | |||
32 | spin_lock(lock); | ||
33 | if (atomic_dec_and_test(atomic)) | ||
34 | return 1; | ||
35 | spin_unlock(lock); | ||
36 | return 0; | ||
37 | } | ||
38 | #else | ||
5 | /* | 39 | /* |
6 | * This is an architecture-neutral, but slow, | 40 | * This is an architecture-neutral, but slow, |
7 | * implementation of the notion of "decrement | 41 | * implementation of the notion of "decrement |
@@ -33,5 +67,6 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) | |||
33 | spin_unlock(lock); | 67 | spin_unlock(lock); |
34 | return 0; | 68 | return 0; |
35 | } | 69 | } |
70 | #endif | ||
36 | 71 | ||
37 | EXPORT_SYMBOL(_atomic_dec_and_lock); | 72 | EXPORT_SYMBOL(_atomic_dec_and_lock); |