On Fri, May 03, 2019 at 10:47:37AM -0700, tip-bot for Nicholas Piggin wrote:
> Commit-ID: 9219565aa89033a9cfdae788c1940473a1253d6c
> Gitweb: https://git.kernel.org/tip/9219565aa89033a9cfdae788c1940473a1253d6c
> Author: Nicholas Piggin <npiggin@xxxxxxxxx>
> AuthorDate: Thu, 11 Apr 2019 13:34:47 +1000
> Committer: Ingo Molnar <mingo@xxxxxxxxxx>
> CommitDate: Fri, 3 May 2019 19:42:58 +0200
>
> sched/isolation: Require a present CPU in housekeeping mask
>
> During housekeeping mask setup, currently a possible CPU is required.
> That does not guarantee the CPU would be available at boot time, so
> check to ensure that at least one present CPU is in the mask.
>
> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Rafael J . Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Link: https://lkml.kernel.org/r/20190411033448.20842-5-npiggin@xxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
> kernel/sched/isolation.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index b02d148e7672..687302051a27 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -65,6 +65,7 @@ void __init housekeeping_init(void)
> static int __init housekeeping_setup(char *str, enum hk_flags flags)
> {
> cpumask_var_t non_housekeeping_mask;
> + cpumask_var_t tmp;
> int err;
>
> alloc_bootmem_cpumask_var(&non_housekeeping_mask);
> @@ -75,16 +76,23 @@ static int __init housekeeping_setup(char *str, enum hk_flags flags)
> return 0;
> }
>
> + alloc_bootmem_cpumask_var(&tmp);
> if (!housekeeping_flags) {
> alloc_bootmem_cpumask_var(&housekeeping_mask);
> cpumask_andnot(housekeeping_mask,
> cpu_possible_mask, non_housekeeping_mask);
> - if (cpumask_empty(housekeeping_mask))
> +
> + cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
> + if (cpumask_empty(tmp)) {
> + pr_warn("Housekeeping: must include one present CPU, "
> + "using boot CPU:%d\n", smp_processor_id());
> __cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
> + __cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
Ah that line (along with its twin below) is actually also a fix for the upstream code.
If the housekeeping mask is empty and we force the current one, we must make sure that
the current CPU is excluded from the nohz_full set. Ideally it should have come as a
separate patch but it's nice that you fixed it anyway.
Thanks!
Acked-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
> + }
> } else {
> - cpumask_var_t tmp;
> -
> - alloc_bootmem_cpumask_var(&tmp);
> + cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
> + if (cpumask_empty(tmp))
> + __cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
> cpumask_andnot(tmp, cpu_possible_mask, non_housekeeping_mask);
> if (!cpumask_equal(tmp, housekeeping_mask)) {
> pr_warn("Housekeeping: nohz_full= must match isolcpus=\n");
> @@ -92,8 +100,8 @@ static int __init housekeeping_setup(char *str, enum hk_flags flags)
> free_bootmem_cpumask_var(non_housekeeping_mask);
> return 0;
> }
> - free_bootmem_cpumask_var(tmp);
> }
> + free_bootmem_cpumask_var(tmp);
>
> if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
> if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
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