releases/4.19.34/sched-debug-initialize-sd_sysctl_cpus-if-config_cpum.patch

   1 From 58bbfbca388e97b886247d17f2f5c3c98adc7776 Mon Sep 17 00:00:00 2001
   2 From: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
   3 Date: Tue, 29 Jan 2019 10:12:45 -0500
   4 Subject: sched/debug: Initialize sd_sysctl_cpus if !CONFIG_CPUMASK_OFFSTACK
   5
   6 [ Upstream commit 1ca4fa3ab604734e38e2a3000c9abf788512ffa7 ]
   7
   8 register_sched_domain_sysctl() copies the cpu_possible_mask into
   9 sd_sysctl_cpus, but only if sd_sysctl_cpus hasn't already been
  10 allocated (ie, CONFIG_CPUMASK_OFFSTACK is set).  However, when
  11 CONFIG_CPUMASK_OFFSTACK is not set, sd_sysctl_cpus is left
  12 uninitialized (all zeroes) and the kernel may fail to initialize
  13 sched_domain sysctl entries for all possible CPUs.
  14
  15 This is visible to the user if the kernel is booted with maxcpus=n, or
  16 if ACPI tables have been modified to leave CPUs offline, and then
  17 checking for missing /proc/sys/kernel/sched_domain/cpu* entries.
  18
  19 Fix this by separating the allocation and initialization, and adding a
  20 flag to initialize the possible CPU entries while system booting only.
  21
  22 Tested-by: Syuuichirou Ishii <ishii.shuuichir@jp.fujitsu.com>
  23 Tested-by: Tarumizu, Kohei <tarumizu.kohei@jp.fujitsu.com>
  24 Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
  25 Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
  26 Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
  27 Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
  28 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  29 Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
  30 Cc: Mike Galbraith <efault@gmx.de>
  31 Cc: Peter Zijlstra <peterz@infradead.org>
  32 Cc: Thomas Gleixner <tglx@linutronix.de>
  33 Link: https://lkml.kernel.org/r/20190129151245.5073-1-msys.mizuma@gmail.com
  34 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  35 Signed-off-by: Sasha Levin <sashal@kernel.org>
  36 ---
  37  kernel/sched/debug.c | 4 ++++
  38  1 file changed, 4 insertions(+)
  39
  40 diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
  41 index 6383aa6a60ca..141ea9ff210e 100644
  42 --- a/kernel/sched/debug.c
  43 +++ b/kernel/sched/debug.c
  44 @@ -315,6 +315,7 @@ void register_sched_domain_sysctl(void)
  45  {
  46         static struct ctl_table *cpu_entries;
  47         static struct ctl_table **cpu_idx;
  48 +       static bool init_done = false;
  49         char buf[32];
  50         int i;
  51
  52 @@ -344,7 +345,10 @@ void register_sched_domain_sysctl(void)
  53         if (!cpumask_available(sd_sysctl_cpus)) {
  54                 if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL))
  55                         return;
  56 +       }
  57
  58 +       if (!init_done) {
  59 +               init_done = true;
  60                 /* init to possible to not have holes in @cpu_entries */
  61                 cpumask_copy(sd_sysctl_cpus, cpu_possible_mask);
  62         }
  63 --
  64 2.19.1
  65