1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
47 lines
1.2 KiB
C
47 lines
1.2 KiB
C
#include <linux/module.h>
|
|
#include <linux/spinlock.h>
|
|
#include <asm/atomic.h>
|
|
#include <asm/system.h>
|
|
|
|
/*
|
|
* 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).
|
|
*
|
|
* N.B. ATOMIC_DEC_AND_LOCK gets defined in include/linux/spinlock.h
|
|
* if spinlocks are empty and thus atomic_dec_and_lock is defined
|
|
* to be atomic_dec_and_test - in that case we don't need it
|
|
* defined here as well.
|
|
*/
|
|
|
|
#ifndef ATOMIC_DEC_AND_LOCK
|
|
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;
|
|
}
|
|
|
|
EXPORT_SYMBOL(_atomic_dec_and_lock);
|
|
#endif /* ATOMIC_DEC_AND_LOCK */
|