Re: [RFC PATCH] kernel: allow to configure PREEMPT_NONE, PREEMPT_VOLUNTARY on kernel command line

Michal Hocko
2020-10-07T12:35:59Z

On Wed 07-10-20 14:21:44, Peter Zijlstra wrote:
> On Wed, Oct 07, 2020 at 02:04:01PM +0200, Michal Hocko wrote:
> > I wanted to make sure that the idea is sound for maintainers first. The
> > next step would be extending the command line to support full preemption
> > as well but there is much more work in that area. Frederic has promissed
> > to look into that.
>
> The sanest way there is to static_call() __preempt_schedule() I think.

Yes, I have checked the code and identified few other places like
irqentry_exit_cond_resched. We also need unconditional
CONFIG_PREEMPT_COUNT IIUC and there are quite some places guarded by
CONFIG_PREEMPTION that would need to be examined. Some of them are
likely pretending to be more clever than they really are/should be -
e.g. mm/slub.c. So there is likely a lot of leg work.
--
Michal Hocko
SUSE Labs