1#include <linux/module.h> 2#include <linux/spinlock.h> 3#include <asm/atomic.h> 4#include <asm/system.h> 5 6/* 7 * This is an implementation of the notion of "decrement a 8 * reference count, and return locked if it decremented to zero". 9 * 10 * This implementation can be used on any architecture that 11 * has a cmpxchg, and where atomic->value is an int holding 12 * the value of the atomic (i.e. the high bits aren't used 13 * for a lock or anything like that). 14 * 15 * N.B. ATOMIC_DEC_AND_LOCK gets defined in include/linux/spinlock.h 16 * if spinlocks are empty and thus atomic_dec_and_lock is defined 17 * to be atomic_dec_and_test - in that case we don't need it 18 * defined here as well. 19 */ 20 21#ifndef ATOMIC_DEC_AND_LOCK 22int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock) 23{ 24 int counter; 25 int newcount; 26 27 for (;;) { 28 counter = atomic_read(atomic); 29 newcount = counter - 1; 30 if (!newcount) 31 break; /* do it the slow way */ 32 33 newcount = cmpxchg(&atomic->counter, counter, newcount); 34 if (newcount == counter) 35 return 0; 36 } 37 38 spin_lock(lock); 39 if (atomic_dec_and_test(atomic)) 40 return 1; 41 spin_unlock(lock); 42 return 0; 43} 44 45EXPORT_SYMBOL(atomic_dec_and_lock); 46#endif /* ATOMIC_DEC_AND_LOCK */ 47