Messages in this thread | | | Subject | Re: [PATCH] sched/debug: initialize sd_sysctl_cpus if !CONFIG_CPUMASK_OFFSTACK | From | Joe Lawrence <> | Date | Fri, 1 Feb 2019 17:33:19 -0500 |
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On 1/31/19 8:44 AM, Masayoshi Mizuma wrote: > On Wed, Jan 30, 2019 at 09:14:00PM +0100, Peter Zijlstra wrote: >> On Tue, Jan 29, 2019 at 10:12:45AM -0500, Masayoshi Mizuma wrote: >>> From: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> >>> >>> 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 allocataion and initialization, and adding >>> a flag to initialize the possible cpu entries while system booting only. >>> >>> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> >>> Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com> >>> Tested-by: Syuuichirou Ishii <ishii.shuuichir@jp.fujitsu.com> >>> Tested-by: Tarumizu, Kohei <tarumizu.kohei@jp.fujitsu.com> >>> --- >>> kernel/sched/debug.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c >>> index de3de997e245..9c6637f3e21d 100644 >>> --- a/kernel/sched/debug.c >>> +++ b/kernel/sched/debug.c >>> @@ -310,6 +310,7 @@ static struct ctl_table *sd_alloc_ctl_cpu_table(int cpu) >>> >>> static cpumask_var_t sd_sysctl_cpus; >>> static struct ctl_table_header *sd_sysctl_header; >>> +static int register_sched_domain_sysctl_on_boot = 1; >>> >>> void register_sched_domain_sysctl(void) >>> { >>> @@ -344,9 +345,12 @@ void register_sched_domain_sysctl(void) >>> if (!cpumask_available(sd_sysctl_cpus)) { >>> if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL)) >>> return; >>> + } >>> >>> + if (register_sched_domain_sysctl_on_boot) { >>> /* init to possible to not have holes in @cpu_entries */ >>> cpumask_copy(sd_sysctl_cpus, cpu_possible_mask); >>> + register_sched_domain_sysctl_on_boot = 0; >>> } >>> >>> for_each_cpu(i, sd_sysctl_cpus) { >> >> I change it like the below. By keeping the initial value 0 it can go >> into .bss instead of .data. > > Great, thanks! > Should I re-post the patch as v2? > > - Masa >
Peter's revision tests fine on my aarch64 box and would get my ACK, however it ends up getting re-posted :)
Thanks,
-- Joe
>> >> --- 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); >> }
-- Joe
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