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Thu, 11 Nov 2021 00:59:01 -0800 (PST) Received: from elver.google.com ([2a00:79e0:15:13:fd21:69cc:1f2b:9812]) by smtp.gmail.com with ESMTPSA id m36sm2258925wms.25.2021.11.11.00.59.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Nov 2021 00:59:00 -0800 (PST) Date: Thu, 11 Nov 2021 09:58:54 +0100 From: Marco Elver To: Valentin Schneider Subject: Re: [PATCH v2 1/5] preempt: Restore preemption model selection configs Message-ID: References: <20211110202448.4054153-1-valentin.schneider@arm.com> <20211110202448.4054153-2-valentin.schneider@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211110202448.4054153-2-valentin.schneider@arm.com> User-Agent: Mutt/2.0.5 (2021-01-21) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michal Marek , linux-kbuild@vger.kernel.org, Peter Zijlstra , Frederic Weisbecker , Mike Galbraith , Nick Desaulniers , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Paul Mackerras , Steven Rostedt , Masahiro Yamada , linuxppc-dev@lists.ozlabs.org, Ingo Molnar , Dmitry Vyukov Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Nov 10, 2021 at 08:24PM +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 would need to > be updated - right now they'll all end up with the default > CONFIG_PREEMPT_NONE_BEHAVIOUR. > > Rather than touch a good hundred of config files, restore usage of > CONFIG_PREEMPT{_NONE, _VOLUNTARY}. Make them configure: > o The build-time preemption model when !PREEMPT_DYNAMIC > o The default boot-time preemption model when PREEMPT_DYNAMIC > > Add siblings of those configs with the _BUILD suffix to unconditionally > designate the build-time preemption model (PREEMPT_DYNAMIC is built with > the "highest" preemption model it supports, aka PREEMPT). Downstream > configs should by now all be depending / selected by CONFIG_PREEMPTION > rather than CONFIG_PREEMPT, so only a few sites need patching up. > > Signed-off-by: Valentin Schneider Acked-by: Marco Elver Much better, thank you! > --- > include/linux/kernel.h | 2 +- > include/linux/vermagic.h | 2 +- > init/Makefile | 2 +- > kernel/Kconfig.preempt | 42 ++++++++++++++++++++-------------------- > kernel/sched/core.c | 6 +++--- > 5 files changed, 27 insertions(+), 27 deletions(-) > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index 2776423a587e..9c7d774ef809 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_BUILD > > extern int __cond_resched(void); > # define might_resched() __cond_resched() > diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h > index 1eaaa93c37bf..329d63babaeb 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_BUILD > #define MODULE_VERMAGIC_PREEMPT "preempt " > #elif defined(CONFIG_PREEMPT_RT) > #define MODULE_VERMAGIC_PREEMPT "preempt_rt " > diff --git a/init/Makefile b/init/Makefile > index 2846113677ee..04eeee12c076 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)" "$(CONFIG_PREEMPT_BUILD)" \ > "$(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..ce77f0265660 100644 > --- a/kernel/Kconfig.preempt > +++ b/kernel/Kconfig.preempt > @@ -1,12 +1,23 @@ > # SPDX-License-Identifier: GPL-2.0-only > > +config PREEMPT_NONE_BUILD > + bool > + > +config PREEMPT_VOLUNTARY_BUILD > + bool > + > +config PREEMPT_BUILD > + bool > + select PREEMPTION > + select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK > + > choice > prompt "Preemption Model" > - default PREEMPT_NONE_BEHAVIOUR > + default PREEMPT_NONE > > -config PREEMPT_NONE_BEHAVIOUR > +config PREEMPT_NONE > bool "No Forced Preemption (Server)" > - select PREEMPT_NONE if !PREEMPT_DYNAMIC > + select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC > help > This is the traditional Linux preemption model, geared towards > throughput. It will still provide good latencies most of the > @@ -18,10 +29,10 @@ config PREEMPT_NONE_BEHAVIOUR > raw processing power of the kernel, irrespective of scheduling > latencies. > > -config PREEMPT_VOLUNTARY_BEHAVIOUR > +config PREEMPT_VOLUNTARY > bool "Voluntary Kernel Preemption (Desktop)" > depends on !ARCH_NO_PREEMPT > - select PREEMPT_VOLUNTARY if !PREEMPT_DYNAMIC > + select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC > help > This option reduces the latency of the kernel by adding more > "explicit preemption points" to the kernel code. These new > @@ -37,10 +48,10 @@ config PREEMPT_VOLUNTARY_BEHAVIOUR > > Select this if you are building a kernel for a desktop system. > > -config PREEMPT_BEHAVIOUR > +config PREEMPT > bool "Preemptible Kernel (Low-Latency Desktop)" > depends on !ARCH_NO_PREEMPT > - select PREEMPT > + select PREEMPT_BUILD > help > This option reduces the latency of the kernel by making > all kernel code (that is not executing in a critical section) > @@ -58,7 +69,7 @@ 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 +86,6 @@ 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 +95,8 @@ 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_BUILD > default y > help > This option allows to define the preemption model on the kernel > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index f2611b9cf503..97047aa7b6c2 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6625,13 +6625,13 @@ __setup("preempt=", setup_preempt_mode); > static void __init preempt_dynamic_init(void) > { > if (preempt_dynamic_mode == preempt_dynamic_undefined) { > - if (IS_ENABLED(CONFIG_PREEMPT_NONE_BEHAVIOUR)) { > + if (IS_ENABLED(CONFIG_PREEMPT_NONE)) { > sched_dynamic_update(preempt_dynamic_none); > - } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY_BEHAVIOUR)) { > + } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) { > sched_dynamic_update(preempt_dynamic_voluntary); > } else { > /* Default static call setting, nothing to do */ > - WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT_BEHAVIOUR)); > + WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT)); > preempt_dynamic_mode = preempt_dynamic_full; > pr_info("Dynamic Preempt: full\n"); > } > -- > 2.25.1 >