Commit 1ca4fa3a authored Jan 29, 2019 by Hidetoshi Seto Committed by Ingo Molnar Feb 04, 2019

sched/debug: Initialize sd_sysctl_cpus if !CONFIG_CPUMASK_OFFSTACK



register_sched_domain_sysctl() copies the cpu_possible_mask into
sd_sysctl_cpus, but only if sd_sysctl_cpus hasn't already been
allocated (ie, CONFIG_CPUMASK_OFFSTACK is set).  However, when
CONFIG_CPUMASK_OFFSTACK is not set, sd_sysctl_cpus is left
uninitialized (all zeroes) and the kernel may fail to initialize
sched_domain sysctl entries for all possible CPUs.

This is visible to the user if the kernel is booted with maxcpus=n, or
if ACPI tables have been modified to leave CPUs offline, and then
checking for missing /proc/sys/kernel/sched_domain/cpu* entries.

Fix this by separating the allocation and initialization, and adding a
flag to initialize the possible CPU entries while system booting only.

Tested-by: Syuuichirou Ishii <ishii.shuuichir@jp.fujitsu.com>
Tested-by: Tarumizu, Kohei <tarumizu.kohei@jp.fujitsu.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190129151245.5073-1-msys.mizuma@gmail.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 10a35e68

kernel/sched/debug.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -315,6 +315,7 @@ void register_sched_domain_sysctl(void)
		{
		static struct ctl_table *cpu_entries;
		static struct ctl_table **cpu_idx;
		static bool init_done = false;
		char buf[32];
		int i;

		@@ -344,7 +345,10 @@ void register_sched_domain_sysctl(void)
		if (!cpumask_available(sd_sysctl_cpus)) {
		if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL))
		return;
		}

		if (!init_done) {
		init_done = true;
		/* init to possible to not have holes in @cpu_entries */
		cpumask_copy(sd_sysctl_cpus, cpu_possible_mask);
		}

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