From 35772d627b55cc7fb4f33bae57c564a25b3121a9 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 4 Oct 2024 14:46:56 +0200 Subject: [PATCH] sched: Enable PREEMPT_DYNAMIC for PREEMPT_RT In order to enable PREEMPT_DYNAMIC for PREEMPT_RT, remove PREEMPT_RT from the 'Preemption Model' choice. Strictly speaking PREEMPT_RT is not a change in how preemption works, but rather it makes a ton more code preemptible. Notably, take away NONE and VOLUNTARY options for PREEMPT_RT, they make no sense (but are techincally possible). Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Sebastian Andrzej Siewior Link: https://lkml.kernel.org/r/20241007075055.441622332@infradead.org --- kernel/Kconfig.preempt | 12 +++++++----- kernel/sched/core.c | 2 ++ kernel/sched/debug.c | 4 ++-- 3 files changed, 11 insertions(+), 7 deletions(-) diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index 09f06d8964cf..7c1b29a3a491 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -20,6 +20,7 @@ choice config PREEMPT_NONE bool "No Forced Preemption (Server)" + depends on !PREEMPT_RT select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC help This is the traditional Linux preemption model, geared towards @@ -35,6 +36,7 @@ config PREEMPT_NONE config PREEMPT_VOLUNTARY bool "Voluntary Kernel Preemption (Desktop)" depends on !ARCH_NO_PREEMPT + depends on !PREEMPT_RT select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC help This option reduces the latency of the kernel by adding more @@ -54,7 +56,7 @@ config PREEMPT_VOLUNTARY config PREEMPT bool "Preemptible Kernel (Low-Latency Desktop)" depends on !ARCH_NO_PREEMPT - select PREEMPT_BUILD + select PREEMPT_BUILD if !PREEMPT_DYNAMIC help This option reduces the latency of the kernel by making all kernel code (that is not executing in a critical section) @@ -74,7 +76,7 @@ config PREEMPT_LAZY bool "Scheduler controlled preemption model" depends on !ARCH_NO_PREEMPT depends on ARCH_HAS_PREEMPT_LAZY - select PREEMPT_BUILD + select PREEMPT_BUILD if !PREEMPT_DYNAMIC help This option provides a scheduler driven preemption model that is fundamentally similar to full preemption, but is less @@ -82,6 +84,8 @@ config PREEMPT_LAZY reduce lock holder preemption and recover some of the performance gains seen from using Voluntary preemption. +endchoice + config PREEMPT_RT bool "Fully Preemptible Kernel (Real-Time)" depends on EXPERT && ARCH_SUPPORTS_RT @@ -99,8 +103,6 @@ config PREEMPT_RT Select this if you are building a kernel for systems which require real-time guarantees. -endchoice - config PREEMPT_COUNT bool @@ -110,7 +112,7 @@ config PREEMPTION config PREEMPT_DYNAMIC bool "Preemption behaviour defined on boot" - depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT + depends on HAVE_PREEMPT_DYNAMIC select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY select PREEMPT_BUILD default y if HAVE_PREEMPT_DYNAMIC_CALL diff --git a/kernel/sched/core.c b/kernel/sched/core.c index df6a34d27d2b..5c47d70f4204 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7450,11 +7450,13 @@ int preempt_dynamic_mode = preempt_dynamic_undefined; int sched_dynamic_mode(const char *str) { +#ifndef CONFIG_PREEMPT_RT if (!strcmp(str, "none")) return preempt_dynamic_none; if (!strcmp(str, "voluntary")) return preempt_dynamic_voluntary; +#endif if (!strcmp(str, "full")) return preempt_dynamic_full; diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 44a49f90b05f..a48b2a701ec2 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -248,9 +248,9 @@ static int sched_dynamic_show(struct seq_file *m, void *v) "none", "voluntary", "full", "lazy", }; int j = ARRAY_SIZE(preempt_modes) - !IS_ENABLED(CONFIG_ARCH_HAS_PREEMPT_LAZY); - int i; + int i = IS_ENABLED(CONFIG_PREEMPT_RT) * 2; - for (i = 0; i < j; i++) { + for (; i < j; i++) { if (preempt_dynamic_mode == i) seq_puts(m, "("); seq_puts(m, preempt_modes[i]);