linux内核情景分析之锁机制 


  1. /*
  2.  * These are the generic versions of the spinlocks and read-write
  3.  * locks..
  4.  *///自旋锁加锁,irqsave表示把标志寄存器存储起来
  5. #define spin_lock_irqsave(lock, flags)		do { local_irq_save(flags);//关闭本地中断,保存标志位       spin_lock(lock); } while (0)
  6. #define spin_lock_irq(lock)			do { local_irq_disable();         spin_lock(lock); } while (0)
  7. #define spin_lock_bh(lock)			do { local_bh_disable();          spin_lock(lock); } while (0)
  8. //读锁与下面写锁,构成读写锁
  9. #define read_lock_irqsave(lock, flags)		do { local_irq_save(flags);       read_lock(lock); } while (0)
  10. #define read_lock_irq(lock)			do { local_irq_disable();         read_lock(lock); } while (0)
  11. #define read_lock_bh(lock)			do { local_bh_disable();          read_lock(lock); } while (0)
  12. //写锁,与上面构成读写锁
  13. #define write_lock_irqsave(lock, flags)		do { local_irq_save(flags);      write_lock(lock); } while (0)
  14. #define write_lock_irq(lock)			do { local_irq_disable();        write_lock(lock); } while (0)
  15. #define write_lock_bh(lock)			do { local_bh_disable();         write_lock(lock); } while (0)
  16. //自旋锁解锁
  17. #define spin_unlock_irqrestore(lock, flags)	do { spin_unlock(lock);  local_irq_restore(flags); } while (0)
  18. #define spin_unlock_irq(lock)			do { spin_unlock(lock);  local_irq_enable();       } while (0)
  19. #define spin_unlock_bh(lock)			do { spin_unlock(lock);  local_bh_enable();        } while (0)
  20. //读锁解锁
  21. #define read_unlock_irqrestore(lock, flags)	do { read_unlock(lock);  local_irq_restore(flags); } while (0)
  22. #define read_unlock_irq(lock)			do { read_unlock(lock);  local_irq_enable();       } while (0)
  23. #define read_unlock_bh(lock)			do { read_unlock(lock);  local_bh_enable();        } while (0)
  24. //写锁解锁
  25. #define write_unlock_irqrestore(lock, flags)	do { write_unlock(lock); local_irq_restore(flags); } while (0)
  26. #define write_unlock_irq(lock)			do { write_unlock(lock); local_irq_enable();       } while (0)
  27. #define write_unlock_bh(lock)			do { write_unlock(lock); local_bh_enable();        } while (0)

自旋锁加锁解析
  2. static inline void spin_lock(spinlock_t *lock)
  3. {
  4. #if SPINLOCK_DEBUG
  5. 	__label__ here;
  6. here:
  7. 	if (lock->magic != SPINLOCK_MAGIC) {//判断是否等于魔数
  8. printk("eip: %p\n", &&here);
  9. 		BUG();
  10. 	}
  11. #endif
  12. 	__asm__ __volatile__(
  13. 		spin_lock_string
  14. 		:"=m" (lock->lock) : : "memory");
  15. }
其中spin_lock_string为一个宏
  2. #define spin_lock_string \
  3. 	"\n1:\t" \
  4. 	"lock ; decb %0\n\t" \ //将lock->lock减1,指令带lock表示把总线锁住,禁止其他cpu访问
  5. 	"js 2f\n" \//不是非负数,直接进入临界区
  6. 	".section .text.lock,\"ax\"\n" \
  7. 	"2:\t" \
  8. 	"cmpb $0,%0\n\t" \//如果-1结果为负数,那就循环检测
  9. 	"rep;nop\n\t" \
  10. 	"jle 2b\n\t" \//如果检测依旧是负数,跳转到2
  11. 	"jmp 1b\n" \//否则检测
  12. 	".previous"


互斥锁,读写锁,条件变量,自旋锁(用于线程互斥)
信号量,文件锁用于进程同步




来自为知笔记(Wiz)


posted on 2016-10-27 10:54  笨拙的菜鸟  阅读(940)  评论(0)    收藏  举报

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