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author | David S. Miller <davem@davemloft.net> | 2005-09-14 21:47:01 -0700 |
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committer | David S. Miller <davem@davemloft.net> | 2005-09-14 21:47:01 -0700 |
commit | 4db2ce0199f04b6e99999f22e28ef9a0ae5f0d2f (patch) | |
tree | 87a00c97e02a77cdfec517398caa3f1d8f6a2f0d /lib/dec_and_lock.c | |
parent | 4a805e863d6b9466baf7084e1d6fdbe6e0628d8e (diff) | |
download | linux-next-4db2ce0199f04b6e99999f22e28ef9a0ae5f0d2f.tar.gz |
[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/dec_and_lock.c')
-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 @@ #include <linux/module.h> #include <linux/spinlock.h> #include <asm/atomic.h> +#include <asm/system.h> +#ifdef __HAVE_ARCH_CMPXCHG +/* + * This is an implementation of the notion of "decrement a + * reference count, and return locked if it decremented to zero". + * + * This implementation can be used on any architecture that + * has a cmpxchg, and where atomic->value is an int holding + * the value of the atomic (i.e. the high bits aren't used + * for a lock or anything like that). + */ +int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) +{ + int counter; + int newcount; + + for (;;) { + counter = atomic_read(atomic); + newcount = counter - 1; + if (!newcount) + break; /* do it the slow way */ + + newcount = cmpxchg(&atomic->counter, counter, newcount); + if (newcount == counter) + return 0; + } + + spin_lock(lock); + if (atomic_dec_and_test(atomic)) + return 1; + spin_unlock(lock); + return 0; +} +#else /* * This is an architecture-neutral, but slow, * implementation of the notion of "decrement @@ -33,5 +67,6 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) spin_unlock(lock); return 0; } +#endif EXPORT_SYMBOL(_atomic_dec_and_lock); |