linux-kernel - Re: kernel/sched/isolation.c:50: undefined reference to `sched_numa_find

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Message-ID: <20250326093532.GA30181@redhat.com>
Date: Wed, 26 Mar 2025 10:35:33 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: kernel test robot <lkp@...el.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Rich Felker <dalias@...c.org>,
	John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, Phil Auld <pauld@...hat.com>
Subject: Re: kernel/sched/isolation.c:50: undefined reference to
 `sched_numa_find_closest'

On 03/26, kernel test robot wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   2d09a9449ecd9a2b9fdac62408c12ee20b6307d2
> commit: 5097cbcb38e6e0d2627c9dde1985e91d2c9f880e sched/isolation: Prevent boot crash when the boot CPU is nohz_full
> date:   11 months ago
> config: sh-randconfig-r132-20250326 (https://download.01.org/0day-ci/archive/20250326/202503260646.lrUqD3j5-lkp@intel.com/config)
...
> >> kernel/sched/isolation.c:50: undefined reference to `sched_numa_find_closest'

kernel/sched/isolation.c makes no sense without CONFIG_SMP, but

	config CPU_ISOLATION
		bool "CPU isolation"
		depends on SMP || COMPILE_TEST

and .config above has CONFIG_COMPILE_TEST but not CONFIG_SMP.

It also has CONFIG_NUMA, it doesn't depend on CONFIG_SMP in
arch/sh/mm/Kconfig, so isolation.c can't use the dummy version
of sched_numa_find_closest() in kernel/sched/sched.h, and
kernel/sched/build_utility.c doesn't include topology.c without
CONFIG_SMP.

Perhaps we can should simply remove this "|| COMPILE_TEST" ?

Oleg.

--- x/init/Kconfig
+++ x/init/Kconfig
@@ -709,7 +709,7 @@ endmenu # "CPU/Task time and stats accou
 
 config CPU_ISOLATION
 	bool "CPU isolation"
-	depends on SMP || COMPILE_TEST
+	depends on SMP
 	default y
 	help
 	  Make sure that CPUs running critical tasks are not disturbed by