linux-kernel - [PATCH] sched/isolation: Make CPU_ISOLATION depend on SMP or COMPILE

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Date:   Tue,  2 Jan 2018 12:13:10 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Nicolas Pitre <nico@...aro.org>, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH] sched/isolation: Make CPU_ISOLATION depend on SMP or COMPILE_TEST

On uniprocessor systems, critical and non-critical tasks cannot be
isolated, as there is only a single CPU core.  Hence enabling CPU
isolation by default on such systems does not make much sense.

Instead of changing the default for !SMP, fix this by making the feature
depend on SMP, with an override for compile-testing.  Note that its sole
selector (NO_HZ_FULL) already depends on SMP.

This decreases kernel size for a default uniprocessor kernel by ca. 1
KiB.

Fixes: 2c43838c99d9d23f ("sched/isolation: Enable CONFIG_CPU_ISOLATION=y by default")
Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
 init/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/init/Kconfig b/init/Kconfig
index 690a381adee0d164..c1221332e128c700 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -461,6 +461,7 @@ endmenu # "CPU/Task time and stats accounting"

 config CPU_ISOLATION
 	bool "CPU isolation"
+	depends on SMP || COMPILE_TEST
 	default y
 	help
 	  Make sure that CPUs running critical tasks are not disturbed by
-- 
2.7.4