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Subject[PATCH AUTOSEL 4.14 085/123] sched/debug: Initialize sd_sysctl_cpus if !CONFIG_CPUMASK_OFFSTACK
From: Hidetoshi Seto <>

[ Upstream commit 1ca4fa3ab604734e38e2a3000c9abf788512ffa7 ]

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 <>
Tested-by: Tarumizu, Kohei <>
Signed-off-by: Hidetoshi Seto <>
Signed-off-by: Peter Zijlstra (Intel) <>
Reviewed-by: Masayoshi Mizuma <>
Acked-by: Joe Lawrence <>
Cc: Linus Torvalds <>
Cc: Masayoshi Mizuma <>
Cc: Mike Galbraith <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Signed-off-by: Ingo Molnar <>
Signed-off-by: Sasha Levin <>
kernel/sched/debug.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 2f93e4a2d9f6..187c04a34ba1 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -339,6 +339,7 @@ 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;

@@ -368,7 +369,10 @@ void register_sched_domain_sysctl(void)
if (!cpumask_available(sd_sysctl_cpus)) {
if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL))
+ }

+ 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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