Re: [patch V2 17/17] sched: Enable might_sleep() and smp_processor_id() checks early

Thomas Gleixner
2017-05-16T22:46:42Z

On Tue, 16 May 2017, Steven Rostedt wrote:
> On Tue, 16 May 2017 20:42:48 +0200
> Thomas Gleixner <tglx@linutronix.de> wrote:
> > +
> > + /*
> > + * Enable might_sleep() and smp_processor_id() checks.
> > + * They cannot be enabled earlier because with CONFIG_PRREMPT=y
>
> My cat's version of CONFIG_PREEMPT, it's CONFIG_ PRR EMPT!

I don't have a cat and I don't need one for creating typos. I'm perfectly
able to do that myself :)

> > + * kernel_thread() would trigger might_sleep() splats. With
> > + * CONFIG_PREEMPT_VOLUNTARY=y the init task might have scheduled
> > + * already, but it's stuck on the kthreadd_done completion.
> > + */
> > + system_state = SYSTEM_SCHEDULING;
> > +
> > complete(&kthreadd_done);
> >
> > /*
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -6226,8 +6226,10 @@ void ___might_sleep(const char *file, in
> >
> > if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
> > !is_idle_task(current)) ||
> > - system_state != SYSTEM_RUNNING || oops_in_progress)
> > + system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
> > + oops_in_progress)
> > return;
> > +
> > if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
> > return;
> > prev_jiffy = jiffies;
> > --- a/lib/smp_processor_id.c
> > +++ b/lib/smp_processor_id.c
> > @@ -28,7 +28,7 @@ notrace static unsigned int check_preemp
> > /*
> > * It is valid to assume CPU-locality during early bootup:
> > */
> > - if (system_state != SYSTEM_RUNNING)
> > + if (system_state < SYSTEM_SCHEDULING)
>
> Do we want to ignore halting or rebooting too?

I don't think so. After setting those states, interesting stuff like
device_shutdown() gets invoked. We want the coverage there.

Thanks,

tglx