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SubjectRe: [patch 1/1] Kconfig: Introduce CONFIG_PREEMPT_RT
On Mon, 15 Jul 2019 17:04:03 +0200
Thomas Gleixner <tglx@linutronix.de> wrote:

> Add a new entry to the preemption menu which enables the real-time support
> for the kernel. The choice is only enabled when an architecture supports
> it.
>
> It selects PREEMPT as the RT features depend on it. To achieve that the
> existing PREEMPT choice is renamed to PREEMPT_LL which select PREEMPT as
> well.
>
> No functional change.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/Kconfig | 3 +++
> kernel/Kconfig.preempt | 25 +++++++++++++++++++++++--
> 2 files changed, 26 insertions(+), 2 deletions(-)
>
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -809,6 +809,9 @@ config ARCH_NO_COHERENT_DMA_MMAP
> config ARCH_NO_PREEMPT
> bool
>
> +config ARCH_SUPPORTS_RT
> + bool
> +
> config CPU_NO_EFFICIENT_FFS
> def_bool n
>
> --- a/kernel/Kconfig.preempt
> +++ b/kernel/Kconfig.preempt
> @@ -35,10 +35,10 @@ config PREEMPT_VOLUNTARY
>
> Select this if you are building a kernel for a desktop system.
>
> -config PREEMPT
> +config PREEMPT_LL
> bool "Preemptible Kernel (Low-Latency Desktop)"
> depends on !ARCH_NO_PREEMPT
> - select PREEMPT_COUNT
> + select PREEMPT
> select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
> help
> This option reduces the latency of the kernel by making
> @@ -55,7 +55,28 @@ config PREEMPT
> embedded system with latency requirements in the milliseconds
> range.
>
> +config PREEMPT_RT
> + bool "Fully Preemptible Kernel (Real-Time)"
> + depends on EXPERT && ARCH_SUPPORTS_RT

I can't wait to see the CONFIG_ARCH_SUPPORTS_RT added!

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve


> + select PREEMPT
> + help
> + This option turns the kernel into a real-time kernel by replacing
> + various locking primitives (spinlocks, rwlocks, etc) with
> + preemptible priority-inheritance aware variants, enforcing
> + interrupt threading and introducing mechanisms to break up long
> + non-preemtible sections. This makes the kernel, except for very
> + low level and critical code pathes (entry code, scheduler, low
> + level interrupt handling) fully preemtible and brings most
> + execution contexts under scheduler control.
> +
> + Select this if you are building a kernel for systems which
> + require real-time guarantees.
> +
> endchoice
>
> config PREEMPT_COUNT
> bool
> +
> +config PREEMPT
> + bool
> + select PREEMPT_COUNT
>

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