Messages in this thread Patch in this message | | | Subject | Re: [PATCH] sched: Tweak default dynamic preempt mode selection | From | Mike Galbraith <> | Date | Sat, 06 Nov 2021 05:40:30 +0100 |
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On Fri, 2021-11-05 at 10:40 +0000, Valentin Schneider wrote: > Commit c597bfddc9e9 ("sched: Provide Kconfig support for default dynamic > preempt mode") changed the selectable config names for the preemption > model. This means a config file must now select > > CONFIG_PREEMPT_BEHAVIOUR=y > > rather than > > CONFIG_PREEMPT=y > > to get a preemptible kernel. This means all arch config files need to be > updated - right now arm64 defconfig selects CONFIG_PREEMPT=y but ends up > with CONFIG_PREEMPT_NONE_BEHAVIOUR=y. > > Instead, have CONFIG_*PREEMPT be the selectable configs again, and make > them select their _BEHAVIOUR equivalent if CONFIG_PREEMPT_DYNAMIC is set.
Is there any way to get to PREEMPT_RT in the first selection again as well? I had created a behavior entry for RT (below) and inverted the dependency to make it appear in the initial selection again, but that's clearly not gonna fly.
Starting with a 5.15 config, to select RT you currently must first select a model you don't want, then reject PREEMPT_DYNAMIC and you'll be offered the full menu of models immediately. With your patch added, that became worse. After rejecting PREEMPT_DYNAMIC, I had to go through new 5.15+ options before finally being offered the full menu.
-Mike
--- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -56,10 +56,10 @@ config PREEMPT_BEHAVIOUR embedded system with latency requirements in the milliseconds range.
-config PREEMPT_RT +config PREEMPT_RT_BEHAVIOR bool "Fully Preemptible Kernel (Real-Time)" - depends on EXPERT && ARCH_SUPPORTS_RT && !PREEMPT_DYNAMIC - select PREEMPTION + depends on EXPERT && ARCH_SUPPORTS_RT + select PREEMPT_RT help This option turns the kernel into a real-time kernel by replacing various locking primitives (spinlocks, rwlocks, etc.) with @@ -86,6 +86,10 @@ config PREEMPT select PREEMPTION select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
+config PREEMPT_RT + bool + select PREEMPTION + config PREEMPT_COUNT bool
@@ -101,7 +105,7 @@ config PREEMPT_LAZY
config PREEMPT_DYNAMIC bool "Preemption behaviour defined on boot" - depends on HAVE_PREEMPT_DYNAMIC + depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT select PREEMPT default y help
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