Messages in this thread | | | Date | Fri, 9 Oct 2020 12:20:09 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH] kernel: allow to configure PREEMPT_NONE, PREEMPT_VOLUNTARY on kernel command line |
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On Fri, Oct 09, 2020 at 12:14:05PM +0200, Michal Hocko wrote: > On Fri 09-10-20 11:47:41, Peter Zijlstra wrote:
> > That is, work backwards (from PREEMPT back to VOLUNTARY) instead of the > > other way around. > > My original idea was that the config would only define the default > preemption mode. preempt_none parameter would then just act as an > override. That would mean that CONFIG_PREEMPTION would be effectively > gone from the kernel. The reason being that any code outside of the > scheduler shouldn't really care about the preemption mode. I suspect > this will prevent from dubious hacks and provide a more robust code in > the end.
Sure; but the way of arriving at that destination might be easier if you work backwards from PREEMPT=y, because while there _should_ not be dependencies outside of the scheduler, we both know there are.
This also makes your patches independent of the series that makes CONFIG_PREEMPTION unconditional.
It also gives Kconfig space to limit the dynamic thing to archs that have sufficient support (we'll be relying on static_call/static_branch, and not everybody has that implemented in a way that makes it the dynamic change worth-while).
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