__WAKE_UP_SYNC_KEY(9)                     Driver Basics                     __WAKE_UP_SYNC_KEY(9)



NAME
       __wake_up_sync_key - wake up threads blocked on a waitqueue.

SYNOPSIS
       void __wake_up_sync_key(wait_queue_head_t * q, unsigned int mode, int nr_exclusive,
                               void * key);

ARGUMENTS
       q
           the waitqueue

       mode
           which threads

       nr_exclusive
           how many wake-one or wake-many threads to wake up

       key
           opaque value to be passed to wakeup targets

DESCRIPTION
       The sync wakeup differs that the waker knows that it will schedule away soon, so while the
       target thread will be woken up, it will not be migrated to another CPU - ie. the two
       threads are 'synchronized' with each other. This can prevent needless bouncing between
       CPUs.

       On UP it can prevent extra preemption.

       It may be assumed that this function implies a write memory barrier before changing the
       task state if and only if any tasks are woken up.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                     __WAKE_UP_SYNC_KEY(9)