diff options
Diffstat (limited to 'lib/dec_and_lock.c')
| -rw-r--r-- | lib/dec_and_lock.c | 24 |
1 files changed, 9 insertions, 15 deletions
diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c index 6658d81e183..e26278576b3 100644 --- a/lib/dec_and_lock.c +++ b/lib/dec_and_lock.c @@ -1,12 +1,10 @@ -#include <linux/module.h> +#include <linux/export.h> #include <linux/spinlock.h> -#include <asm/atomic.h> +#include <linux/atomic.h> /* - * This is an architecture-neutral, but slow, - * implementation of the notion of "decrement - * a reference count, and return locked if it - * decremented to zero". + * This is an implementation of the notion of "decrement a + * reference count, and return locked if it decremented to zero". * * NOTE NOTE NOTE! This is _not_ equivalent to * @@ -18,17 +16,14 @@ * * because the spin-lock and the decrement must be * "atomic". - * - * This slow version gets the spinlock unconditionally, - * and releases it if it isn't needed. Architectures - * are encouraged to come up with better approaches, - * this is trivially done efficiently using a load-locked - * store-conditional approach, for example. */ - -#ifndef ATOMIC_DEC_AND_LOCK int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) { + /* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */ + if (atomic_add_unless(atomic, -1, 1)) + return 0; + + /* Otherwise do it the slow way */ spin_lock(lock); if (atomic_dec_and_test(atomic)) return 1; @@ -37,4 +32,3 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) } EXPORT_SYMBOL(_atomic_dec_and_lock); -#endif |