From: Hidetoshi Seto <[email protected]> [ 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 <[email protected]> Tested-by: Tarumizu, Kohei <[email protected]> Signed-off-by: Hidetoshi Seto <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Reviewed-by: Masayoshi Mizuma <[email protected]> Acked-by: Joe Lawrence <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Masayoshi Mizuma <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- 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)) 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
