spin_lock_irqsave

spin_lock_irqsave

https://blog.csdn.net/lzn948055097/article/details/120302623

/**
* down - acquire the semaphore
* @sem: the semaphore to be acquired
*
* Acquires the semaphore. If no more tasks are allowed to acquire the
* semaphore, calling this function will put the task to sleep until the
* semaphore is released.
*
* Use of this function is deprecated, please use down_interruptible() or
* down_killable() instead.
*/

Add igmp snooping support