doubt regarding atomic_dec_and_lock kernel function

rajesh_b · 07-11-2006, 09:22 AM

Hi,
I have a doubt regarding the function atomic_dec_and_lock.
the prototype is int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)

My doubt is whether after returning from this function we will obtain the lock irrespective of the counter value ( zero or not zero).
Or is it like that we will obtain lock only when the counter is zero.

Regards
Rajesh

shvechkov · 11-28-2006, 07:39 AM

will take a lock only if counter is 0
(kernel 2.4.22) lib/dec_and_lock.c :

Code:

int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
        spin_lock(lock);
        if (atomic_dec_and_test(atomic))
                return 1;
        spin_unlock(lock);
        return 0;
}