Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | Re: [PATCH] sched: Split preemption model selection between DYNAMIC & !DYNAMIC | Date | Wed, 10 Nov 2021 11:24:48 +0000 |
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On 10/11/21 05:37, Mike Galbraith wrote: > On Wed, 2021-11-10 at 02:17 +0100, Frederic Weisbecker wrote: >> The problem here is that you're duplicating the existing titles >> for the static entries and you're losing all the help that text that used to come >> along. The point of the BEHAVIOUR thing, further mapping to either >> static or dynamic preemption, was to avoid that duplication and keep the >> same titles and help for the three behaviour, whether static or dynamic. > > Adding "depends on !PREEMPT_DYNAMIC" to the first (legacy?) choice made > it appear/disappear at the appropriate time as well, but I have no idea > how duplication of help text can be avoided. > > -Mike
Following Frederic's _STATIC suggestion, I got to the below. The nice thing is if a defconfig picks say PREEMPT_VOLUNTARY and the arch supports PREEMPT_DYNAMIC, then it'll pick PREEMPT_VOLUNTARY_BEHAVIOUR. The less nice thing is that we end up selecting PREEMPT_STATIC for PREEMPT_DYNAMIC kernels, naming's hard... Maybe _BUILD rather than _STATIC?
--- diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 2776423a587e..1fa8f6fb3c55 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -88,7 +88,7 @@ struct completion; struct user; -#ifdef CONFIG_PREEMPT_VOLUNTARY +#ifdef CONFIG_PREEMPT_VOLUNTARY_STATIC extern int __cond_resched(void); # define might_resched() __cond_resched() diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h index 1eaaa93c37bf..0a311d7aab62 100644 --- a/include/linux/vermagic.h +++ b/include/linux/vermagic.h @@ -15,7 +15,7 @@ #else #define MODULE_VERMAGIC_SMP "" #endif -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_STATIC #define MODULE_VERMAGIC_PREEMPT "preempt " #elif defined(CONFIG_PREEMPT_RT) #define MODULE_VERMAGIC_PREEMPT "preempt_rt " @@ -39,9 +39,9 @@ #define MODULE_RANDSTRUCT_PLUGIN #endif -#define VERMAGIC_STRING \ +#define VERMAGIC_STRING \ UTS_RELEASE " " \ - MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT \ + MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT \ MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS \ MODULE_ARCH_VERMAGIC \ MODULE_RANDSTRUCT_PLUGIN diff --git a/init/Makefile b/init/Makefile index 2846113677ee..989f43d23b83 100644 --- a/init/Makefile +++ b/init/Makefile @@ -30,7 +30,7 @@ $(obj)/version.o: include/generated/compile.h quiet_cmd_compile.h = CHK $@ cmd_compile.h = \ $(CONFIG_SHELL) $(srctree)/scripts/mkcompile_h $@ \ - "$(UTS_MACHINE)" "$(CONFIG_SMP)" "$(CONFIG_PREEMPT)" \ + "$(UTS_MACHINE)" "$(CONFIG_SMP)" "$(CONFIG_PREEMPT_STATIC)" \ "$(CONFIG_PREEMPT_RT)" $(CONFIG_CC_VERSION_TEXT) "$(LD)" include/generated/compile.h: FORCE diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index 60f1bfc3c7b2..1761966c815e 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -1,12 +1,40 @@ # SPDX-License-Identifier: GPL-2.0-only + +choice + prompt "[Legacy compatibility] Preemption Model" + +config PREEMPT_NONE + bool "No Forced Preemption (Server)" + +config PREEMPT_VOLUNTARY + bool "Voluntary Kernel Preemption (Desktop)" + +config PREEMPT + bool "Preemptible Kernel (Low-Latency Desktop)" + +endchoice + +config PREEMPT_NONE_STATIC + bool + +config PREEMPT_VOLUNTARY_STATIC + bool + +config PREEMPT_STATIC + bool + select PREEMPTION + select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK + choice prompt "Preemption Model" + default PREEMPT_BEHAVIOUR if PREEMPT + default PREEMPT_VOLUNTARY_BEHAVIOUR if PREEMPT_VOLUNTARY default PREEMPT_NONE_BEHAVIOUR config PREEMPT_NONE_BEHAVIOUR bool "No Forced Preemption (Server)" - select PREEMPT_NONE if !PREEMPT_DYNAMIC + select PREEMPT_NONE_STATIC if !PREEMPT_DYNAMIC help This is the traditional Linux preemption model, geared towards throughput. It will still provide good latencies most of the @@ -21,7 +49,7 @@ config PREEMPT_NONE_BEHAVIOUR config PREEMPT_VOLUNTARY_BEHAVIOUR bool "Voluntary Kernel Preemption (Desktop)" depends on !ARCH_NO_PREEMPT - select PREEMPT_VOLUNTARY if !PREEMPT_DYNAMIC + select PREEMPT_VOLUNTARY_STATIC if !PREEMPT_DYNAMIC help This option reduces the latency of the kernel by adding more "explicit preemption points" to the kernel code. These new @@ -40,7 +68,7 @@ config PREEMPT_VOLUNTARY_BEHAVIOUR config PREEMPT_BEHAVIOUR bool "Preemptible Kernel (Low-Latency Desktop)" depends on !ARCH_NO_PREEMPT - select PREEMPT + select PREEMPT_STATIC help This option reduces the latency of the kernel by making all kernel code (that is not executing in a critical section) @@ -58,7 +86,7 @@ config PREEMPT_BEHAVIOUR config PREEMPT_RT bool "Fully Preemptible Kernel (Real-Time)" - depends on EXPERT && ARCH_SUPPORTS_RT && !PREEMPT_DYNAMIC + depends on EXPERT && ARCH_SUPPORTS_RT select PREEMPTION help This option turns the kernel into a real-time kernel by replacing @@ -75,17 +103,6 @@ config PREEMPT_RT endchoice -config PREEMPT_NONE - bool - -config PREEMPT_VOLUNTARY - bool - -config PREEMPT - bool - select PREEMPTION - select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK - config PREEMPT_COUNT bool @@ -95,8 +112,8 @@ config PREEMPTION config PREEMPT_DYNAMIC bool "Preemption behaviour defined on boot" - depends on HAVE_PREEMPT_DYNAMIC - select PREEMPT + depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT + select PREEMPT_STATIC default y help This option allows to define the preemption model on the kernel diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c index dc55fd5a36fc..83dd9e6a8235 100644 --- a/kernel/kcsan/kcsan_test.c +++ b/kernel/kcsan/kcsan_test.c @@ -1005,13 +1005,13 @@ static const void *nthreads_gen_params(const void *prev, char *desc) else nthreads *= 2; - if (!IS_ENABLED(CONFIG_PREEMPT) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) { + if (!IS_ENABLED(CONFIG_PREEMPTION) || !IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER)) { /* * Without any preemption, keep 2 CPUs free for other tasks, one * of which is the main test case function checking for * completion or failure. */ - const long min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE) ? 2 : 0; + const long min_unused_cpus = IS_ENABLED(CONFIG_PREEMPT_NONE_STATIC) ? 2 : 0; const long min_required_cpus = 2 + min_unused_cpus; if (num_online_cpus() < min_required_cpus) { diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 7896d30d90f7..67413be56f22 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4271,11 +4271,11 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter) entries, total, buf->cpu, -#if defined(CONFIG_PREEMPT_NONE) +#if defined(CONFIG_PREEMPT_NONE_STATIC) "server", -#elif defined(CONFIG_PREEMPT_VOLUNTARY) +#elif defined(CONFIG_PREEMPT_VOLUNTARY_STATIC) "desktop", -#elif defined(CONFIG_PREEMPT) +#elif defined(CONFIG_PREEMPT_STATIC) "preempt", #elif defined(CONFIG_PREEMPT_RT) "preempt_rt",
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