Revision 436b0f76f2cee6617f27a649637766628909dd5d authored by Linus Torvalds on 04 December 2005, 05:10:42 UTC, committed by Linus Torvalds on 04 December 2005, 05:10:42 UTC
Hey, for no other reason than the fact that I'll be off-line for a week. Of course, I could force everybody to just use git (and when I'm emperor of the world, don't think I won't!), but it seems some people want to just test official releases. Even if they are just -rc's. By the time I'm back, Andrew will have fixed all my bugs, and I'll release it as 2.6.15 and take all the credit. Mwahahahaaa Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1 parent 6015d2c
dec_and_lock.c
#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
* a reference count, and return locked if it
* decremented to zero".
*
* NOTE NOTE NOTE! This is _not_ equivalent to
*
* if (atomic_dec_and_test(&atomic)) {
* spin_lock(&lock);
* return 1;
* }
* return 0;
*
* 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.
*/
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;
}
#endif
EXPORT_SYMBOL(_atomic_dec_and_lock);
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...