Re: [PATCH v3 5/6] sched/wait: Add wait_event_state()

Ingo Molnar
2022-09-07T07:26:36Z

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Sun, Sep 04, 2022 at 11:54:57AM +0200, Ingo Molnar wrote:
> > > +/**
> > > + * wait_event_state - sleep until a condition gets true
> > > + * @wq_head: the waitqueue to wait on
> > > + * @condition: a C expression for the event to wait for
> > > + * @state: state to sleep in
> > > + *
> > > + * The process is put to sleep (@state) until the @condition evaluates to true
> > > + * or a signal is received. The @condition is checked each time the waitqueue
> > > + * @wq_head is woken up.
> >
> > Documentation inconsistency nit: if TASK_INTERRUPTIBLE isn't in @state then
> > we won't wake up when a signal is received. This probably got copy-pasted
> > from a signal variant.
> >
> > > + *
> > > + * wake_up() has to be called after changing any variable that could
> > > + * change the result of the wait condition.
> > > + *
> > > + * The function will return -ERESTARTSYS if it was interrupted by a
> > > + * signal and 0 if @condition evaluated to true.
> >
> > That's not unconditionally true either if !TASK_INTERRUPTIBLE.
>
>
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -942,14 +942,14 @@ extern int do_wait_intr_irq(wait_queue_h
> * @state: state to sleep in
> *
> * The process is put to sleep (@state) until the @condition evaluates to true
> - * or a signal is received. The @condition is checked each time the waitqueue
> - * @wq_head is woken up.
> + * or a signal is received (when allowed by @state). The @condition is checked
> + * each time the waitqueue @wq_head is woken up.
> *
> * wake_up() has to be called after changing any variable that could
> * change the result of the wait condition.
> *
> - * The function will return -ERESTARTSYS if it was interrupted by a
> - * signal and 0 if @condition evaluated to true.
> + * The function will return -ERESTARTSYS if it was interrupted by a signal
> + * (when allowed by @state) and 0 if @condition evaluated to true.
> */

Reviewed-by: Ingo Molnar <mingo@kernel.org>

> > > +#define wait_event_state(wq_head, condition, state) \
> > > +({ \
> > > + int __ret = 0; \
> > > + \
> > > + might_sleep(); \
> >
> > Like most (but not all ... :-/ ) of the existing primitives have.
>
> Yeah, I'm going to leave it as is.

Will queue up a cleanup patch, should I ever notice this detail again ... :-)

Thanks,

Ingo