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本人在学习内核源代码内存模块(2。4。2)时,发现spin_lock有多种实现。
其中一种:
#define DEBUG_SPINLOCKS 0 /* 0 == no debugging, 1 == maintain lock state, 2 == full debug */
#if (DEBUG_SPINLOCKS < 1)
#define spin_lock(lock) (void)(lock) /* Not "unused variable". */
#elif (DEBUG_SPINLOCKS < 2)
#define spin_lock(x) do { (x)->;lock = 1; } while (0)
#else /* (DEBUG_SPINLOCKS >;= 2) */
#define spin_lock(x)
do {unsigned long __spinflags; save_flags(__spinflags); cli(); if ((x)->;lock&&(x)->;babble) {printk("%s:%d: spin_lock(%s:%p) already locked\n", __BASE_FILE__,__LINE__, (x)->;module, (x));(x)->;babble--;} (x)->;lock = 1; restore_flags(__spinflags);} while (0)
#endif
理解如下:
随着DEBUG_SPINLOCKS取植不同,函数有不同定义。好象只在其为2时,才调用cli关中断。其余情况
没有实际用途。请问我理解正确?
另外一种:
include\asm-i386\spinlock.h
static inline void spin_lock(spinlock_t *lock)
{
#if SPINLOCK_DEBUG
__label__ here;
here:
if (lock->;magic != SPINLOCK_MAGIC) {
printk("eip: %p\n", &&here);
BUG();
}
#endif
__asm__ __volatile__(
spin_lock_string
:"=m" (lock->;lock) : : "memory"
}
不太理解,请指教! |
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