Man page 9 : wait_event_timeout

wait_event_timeout - sleep until a condition gets true or a timeout elapses

wait_event_timeout( wq , condition , timeout );

wq
    the waitqueue to wait on

condition
    a C expression for the event to wait for

timeout
    timeout, in jiffies

The process is put to sleep (TASK_UNINTERRUPTIBLE) until the condition evaluates to true. The condition is checked each time the waitqueue wq is woken up.

wake_up has to be called after changing any variable that could change the result of the wait condition.

The function returns 0 if the timeout elapsed, or the remaining jiffies (at least 1) if the condition evaluated to true before the timeout elapsed.