#include <linux/module.h> #include <linux/spinlock.h> #include <asm/atomic.h> /* * 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. */ #ifndef ATOMIC_DEC_AND_LOCK 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; } EXPORT_SYMBOL(_atomic_dec_and_lock); #endif