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 <[email protected]> Acked-by: Paul E. McKenney <[email protected]> Acked-by: Steven Rostedt (VMware) <[email protected]> Acked-by: Clark Williams <[email protected]> Acked-by: Daniel Bristot de Oliveira <[email protected]> Acked-by: Frederic Weisbecker <[email protected]> Acked-by: Ingo Molnar <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Marc Zyngier <[email protected]> Acked-by: Daniel Wagner <[email protected]> --- V2: Fix typos in help text, collect acks --- 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 + 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-preemptible sections. This makes the kernel, except for very + low level and critical code pathes (entry code, scheduler, low + level interrupt handling) fully preemptible 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
