Question

I wonder how can I use wake_up_interruptible, if it returns void: http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/include/linux/wait.h#L161 (_wake_up function returns void). For example, down_interruptible function returns int: http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/kernel/semaphore.c#L75 This allows to write such code, for example:

if ( down_interruptible(&dev->sem) )
    return -ERESTARTSYS;
// continue: down_interruptible succeeded

When I call wake_up_interruptible, and it is interrupted, how can I know this, if it returns void?

Answer 1

i suppose normal usage scenario would be, in one thread:

for (;;) {
   wait_event_interruptible(wait_queue, condition);
   /* Some processing */
}

and from some other thread:

if (something_happened)
   wake_up_interruptible(wait_queue);

which will result in one process from wait_queue which is in TASK_INTERRUPTIBLE state to be woken up and evalueate condition

see some more examples here, a bit dated bit gives an idea