From: Xiongfeng Wang <wangxiongfeng2@huawei.com> hulk inclusion category: feature bugzilla: https://atomgit.com/openeuler/kernel/issues/9856 -------------------------------- If we set isolcpus including CPU0, it will print the following error: [ 0.000000] Housekeeping: must include one present CPU, using boot CPU:0 It is because when string 'isolcpus=xxx' is parsed, only CPU0 is set as present for arch arm64. Unlike X86 and PowerPC, the present_cpu_mask is set rather late in smp_prepare_cpus() for arm64. In CPU hotplug situation, some possible CPUs are not marked as present, only CPUs with its GICC marked as ACPI_MADT_ENABLED are marked as present. So we cannot set preset_cpu_mask for all possible CPUs at early stage. Only check cpu_present_mask cannot assure that the CPUs will be broughtup online, as described in the below Link1. So do not check whether housekeeping CPUs are present when parsing 'isolcpus'. A following commit will add check after CPU online process is finished, as suggested in below Link2. With the boot CPU allowed to be nohz_full, housekeeping_any_cpu() can return an invalid CPU number at boot time before start_secondary() brings the 1st housekeeping CPU up, which crashes the kernel when the value is used as a per-CPU index by get_nohz_timer_target()'s callers (timer.c/hrtimer.c get_target_base()). This is the code part of the upstream fix 5097cbcb38e6 ("sched/isolation: Prevent boot crash when the boot CPU is nohz_full"), which was stripped from the LTS backport already merged into this tree (only the documentation part was taken). Include it here since this series makes 'nohz_full=' masks including the boot CPU reachable on arm64. Link: https://lore.kernel.org/all/20190504002733.GB19076@lenoir/ Link: https://lore.kernel.org/all/1557186148.ocs72ssdjc.astroid@bobo.none/ Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com> Signed-off-by: Xia Fukun <xiafukun@huawei.com> --- include/linux/tick.h | 2 ++ kernel/sched/isolation.c | 37 +++++++++++++++++++++++++++++-------- kernel/time/tick-sched.c | 9 +++++++++ 3 files changed, 40 insertions(+), 8 deletions(-) diff --git a/include/linux/tick.h b/include/linux/tick.h index 39f01f0bef76..5c929c429007 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -42,8 +42,10 @@ extern void tick_irq_enter(void); # ifndef arch_needs_cpu # define arch_needs_cpu() (0) # endif +extern bool support_cpu0_nohz_full; # else static inline void tick_irq_enter(void) { } +#define support_cpu0_nohz_full 0 #endif #if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_TICK_ONESHOT) diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 1179dc21873e..e2d6a88611dc 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -46,7 +46,16 @@ int housekeeping_any_cpu(enum hk_type type) if (cpu < nr_cpu_ids) return cpu; - return cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask); + cpu = cpumask_any_and(housekeeping.cpumasks[type], cpu_online_mask); + if (likely(cpu < nr_cpu_ids)) + return cpu; + /* + * Unless we have another problem this can only happen + * at boot time before start_secondary() brings the 1st + * housekeeping CPU up. + */ + WARN_ON_ONCE(system_state == SYSTEM_RUNNING || + type != HK_TYPE_TIMER); } } return smp_processor_id(); @@ -130,13 +139,25 @@ static int __init housekeeping_setup(char *str, unsigned long flags) cpumask_andnot(housekeeping_staging, cpu_possible_mask, non_housekeeping_mask); - first_cpu = cpumask_first_and(cpu_present_mask, housekeeping_staging); - if (first_cpu >= nr_cpu_ids || first_cpu >= setup_max_cpus) { - __cpumask_set_cpu(smp_processor_id(), housekeeping_staging); - __cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask); - if (!housekeeping.flags) { - pr_warn("Housekeeping: must include one present CPU, " - "using boot CPU:%d\n", smp_processor_id()); + if (support_cpu0_nohz_full) { + if (cpumask_empty(housekeeping_staging)) { + pr_warn("Housekeeping cpumask is NULL, using boot CPU\n"); + __cpumask_set_cpu(smp_processor_id(), housekeeping_staging); + /* Update non_housekeeping_mask to reflect this change */ + cpumask_andnot(non_housekeeping_mask, + cpu_possible_mask, housekeeping_staging); + } + /* No need to check against cpu_present_mask here */ + first_cpu = smp_processor_id(); + } else { + first_cpu = cpumask_first_and(cpu_present_mask, housekeeping_staging); + if (first_cpu >= nr_cpu_ids || first_cpu >= setup_max_cpus) { + __cpumask_set_cpu(smp_processor_id(), housekeeping_staging); + __cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask); + if (!housekeeping.flags) { + pr_warn("Housekeeping: must include one present CPU, " + "using boot CPU:%d\n", smp_processor_id()); + } } } diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 55cbc49f70d1..33a471692def 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -38,6 +38,8 @@ */ static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); +bool support_cpu0_nohz_full; + struct tick_sched *tick_get_tick_sched(int cpu) { return &per_cpu(tick_cpu_sched, cpu); @@ -1615,3 +1617,10 @@ int tick_check_oneshot_change(int allow_nohz) tick_nohz_switch_to_nohz(); return 0; } + +static int __init support_cpu0_nohz_full_setup(char *str) +{ + support_cpu0_nohz_full = true; + return 0; +} +early_param("support_cpu0_nohz_full", support_cpu0_nohz_full_setup); -- 2.34.1