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Message-Id: <20211110202448.4054153-2-valentin.schneider@arm.com>
Date: Wed, 10 Nov 2021 20:24:44 +0000
From: Valentin Schneider <valentin.schneider@....com>
To: linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
linuxppc-dev@...ts.ozlabs.org, linux-kbuild@...r.kernel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Frederic Weisbecker <frederic@...nel.org>,
Mike Galbraith <efault@....de>, Marco Elver <elver@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Steven Rostedt <rostedt@...dmis.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH v2 1/5] preempt: Restore preemption model selection configs
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 <valentin.schneider@....com>
---
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
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