sched/isolation: Make CONFIG_CPU_ISOLATION=y 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.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 2c43838c99d9d23f ("sched/isolation: Enable CONFIG_CPU_ISOLATION=y by default")
Link: http://lkml.kernel.org/r/1514891590-20782-1-git-send-email-geert@linux-m68k.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/init/Kconfig b/init/Kconfig
index 690a381adee0d164f52c9984f61c0d710c54c089..c1221332e128c7004e5cd60f5596f5b857c4950e 100644 (file)
--- 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