Re: [PATCHv3 2/6] tty/ldsem: Update waiter->task before waking up reader

[Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>]

On (09/11/18 14:04), Sergey Senozhatsky wrote:
> >  	for (;;) {
> >  		set_current_state(TASK_UNINTERRUPTIBLE);
> 
> I think that set_current_state() also executes memory barrier. Just
> because it accesses task state.
> 
> > -		if (!waiter.task)
> > +		if (!READ_ONCE(waiter.task))
> >  			break;
> >  		if (!timeout)
> >  			break;

This READ_ONCE(waiter.task) looks interesting. Maybe could be moved
to a loop condition

	while (!READ_ONCE(waiter.task)) {
		...
	}

	-ss