/arch/ppc64/lib/dec_and_lock.c
https://bitbucket.org/evzijst/gittest · C · 55 lines · 26 code · 7 blank · 22 comment · 5 complexity · 76503f4c2e65b069efffa1125f22eeb7 MD5 · raw file
- /*
- * ppc64 version of atomic_dec_and_lock() using cmpxchg
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
- #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 */