[PATCH] ARM: support PREEMPT_DYNAMIC

[Russell King (Oracle)]

On Wed, Jul 31, 2024 at 10:07:53AM +0800, Jinjie Ruan wrote:
> On 2024/6/20 17:00, Jinjie Ruan wrote:
> > Enable support for PREEMPT_DYNAMIC on arm32, allowing the preemption model
> > to be chosen at boot time.
> > 
> > Similar to arm64, arm32 does not yet use the generic entry code, we must
> > define our own `sk_dynamic_irqentry_exit_cond_resched`, which will be
> > enabled/disabled by the common code in kernel/sched/core.c.
> > 
> > And arm32 use generic preempt.h, so declare
> > `sk_dynamic_irqentry_exit_cond_resched` if the arch do not use generic
> > entry. Other architectures which use generic preempt.h but not use generic
> > entry can benefit from it.
> > 
> > Test ok with the below cmdline parameters on Qemu versatilepb board:
> > 	`preempt=none`
> > 	`preempt=voluntary`
> > 	`preempt=full`
> > 
> > Update preempt mode with debugfs interface on above Qemu board is also
> > tested ok:
> > 	# cd /sys/kernel/debug/sched
> > 	# echo none > preempt
> > 	# echo voluntary > preempt
> > 	# echo full > preempt

Do you have a use case for this feature?

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