RE: [PATCH] kfence: use TASK_IDLE when awaiting allocation

[David Laight]

From: Marco Elver
> Sent: 21 May 2021 10:48
> 
> On Fri, May 21, 2021 at 09:39AM +0000, David Laight wrote:
> > From: Marco Elver
> > > Sent: 21 May 2021 09:32
> > >
> > > Since wait_event() uses TASK_UNINTERRUPTIBLE by default, waiting for an
> > > allocation counts towards load. However, for KFENCE, this does not make
> > > any sense, since there is no busy work we're awaiting.
> > >
> > > Instead, use TASK_IDLE via wait_event_idle() to not count towards load.
> >
> > Doesn't that let the process be interruptible by a signal.
> > Which is probably not desirable.
> >
> > There really ought to be a way of sleeping with TASK_UNINTERRUPTIBLE
> > without changing the load-average.
> 
> That's what TASK_IDLE is:
> 
> 	include/linux/sched.h:#define TASK_IDLE                 (TASK_UNINTERRUPTIBLE | TASK_NOLOAD)

That's been added since I last tried to stop tasks updating
the load-average :-)

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)