From: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx> [ 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 <ishii.shuuichir@xxxxxxxxxxxxxx> Tested-by: Tarumizu, Kohei <tarumizu.kohei@xxxxxxxxxxxxxx> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> Acked-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Masayoshi Mizuma <msys.mizuma@xxxxxxxxx> Cc: Mike Galbraith <efault@xxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20190129151245.5073-1-msys.mizuma@xxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/sched/debug.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index de3de997e245..8039d62ae36e 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -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); } -- 2.19.1
