kernel/sched/isolation.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  Housekeeping management. Manage the targets for routine code that can run on
   4  *  any CPU: unbound workqueues, timers, kthreads and any offloadable work.
   5  *
   6  * Copyright (C) 2017 Red Hat, Inc., Frederic Weisbecker
   7  * Copyright (C) 2017-2018 SUSE, Frederic Weisbecker
   8  *
   9  */
  10 #include "sched.h"
  11
  12 DEFINE_STATIC_KEY_FALSE(housekeeping_overridden);
  13 EXPORT_SYMBOL_GPL(housekeeping_overridden);
  14 static cpumask_var_t housekeeping_mask;
  15 static unsigned int housekeeping_flags;
  16
  17 bool housekeeping_enabled(enum hk_flags flags)
  18 {
  19         return !!(housekeeping_flags & flags);
  20 }
  21 EXPORT_SYMBOL_GPL(housekeeping_enabled);
  22
  23 int housekeeping_any_cpu(enum hk_flags flags)
  24 {
  25         if (static_branch_unlikely(&housekeeping_overridden))
  26                 if (housekeeping_flags & flags)
  27                         return cpumask_any_and(housekeeping_mask, cpu_online_mask);
  28         return smp_processor_id();
  29 }
  30 EXPORT_SYMBOL_GPL(housekeeping_any_cpu);
  31
  32 const struct cpumask *housekeeping_cpumask(enum hk_flags flags)
  33 {
  34         if (static_branch_unlikely(&housekeeping_overridden))
  35                 if (housekeeping_flags & flags)
  36                         return housekeeping_mask;
  37         return cpu_possible_mask;
  38 }
  39 EXPORT_SYMBOL_GPL(housekeeping_cpumask);
  40
  41 void housekeeping_affine(struct task_struct *t, enum hk_flags flags)
  42 {
  43         if (static_branch_unlikely(&housekeeping_overridden))
  44                 if (housekeeping_flags & flags)
  45                         set_cpus_allowed_ptr(t, housekeeping_mask);
  46 }
  47 EXPORT_SYMBOL_GPL(housekeeping_affine);
  48
  49 bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
  50 {
  51         if (static_branch_unlikely(&housekeeping_overridden))
  52                 if (housekeeping_flags & flags)
  53                         return cpumask_test_cpu(cpu, housekeeping_mask);
  54         return true;
  55 }
  56 EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
  57
  58 void __init housekeeping_init(void)
  59 {
  60         if (!housekeeping_flags)
  61                 return;
  62
  63         static_branch_enable(&housekeeping_overridden);
  64
  65         if (housekeeping_flags & HK_FLAG_TICK)
  66                 sched_tick_offload_init();
  67
  68         /* We need at least one CPU to handle housekeeping work */
  69         WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
  70 }
  71
  72 static int __init housekeeping_setup(char *str, enum hk_flags flags)
  73 {
  74         cpumask_var_t non_housekeeping_mask;
  75         cpumask_var_t tmp;
  76         int err;
  77
  78         alloc_bootmem_cpumask_var(&non_housekeeping_mask);
  79         err = cpulist_parse(str, non_housekeeping_mask);
  80         if (err < 0 || cpumask_last(non_housekeeping_mask) >= nr_cpu_ids) {
  81                 pr_warn("Housekeeping: nohz_full= or isolcpus= incorrect CPU range\n");
  82                 free_bootmem_cpumask_var(non_housekeeping_mask);
  83                 return 0;
  84         }
  85
  86         alloc_bootmem_cpumask_var(&tmp);
  87         if (!housekeeping_flags) {
  88                 alloc_bootmem_cpumask_var(&housekeeping_mask);
  89                 cpumask_andnot(housekeeping_mask,
  90                                cpu_possible_mask, non_housekeeping_mask);
  91
  92                 cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
  93                 if (cpumask_empty(tmp)) {
  94                         pr_warn("Housekeeping: must include one present CPU, "
  95                                 "using boot CPU:%d\n", smp_processor_id());
  96                         __cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
  97                         __cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
  98                 }
  99         } else {
 100                 cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
 101                 if (cpumask_empty(tmp))
 102                         __cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
 103                 cpumask_andnot(tmp, cpu_possible_mask, non_housekeeping_mask);
 104                 if (!cpumask_equal(tmp, housekeeping_mask)) {
 105                         pr_warn("Housekeeping: nohz_full= must match isolcpus=\n");
 106                         free_bootmem_cpumask_var(tmp);
 107                         free_bootmem_cpumask_var(non_housekeeping_mask);
 108                         return 0;
 109                 }
 110         }
 111         free_bootmem_cpumask_var(tmp);
 112
 113         if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
 114                 if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
 115                         tick_nohz_full_setup(non_housekeeping_mask);
 116                 } else {
 117                         pr_warn("Housekeeping: nohz unsupported."
 118                                 " Build with CONFIG_NO_HZ_FULL\n");
 119                         free_bootmem_cpumask_var(non_housekeeping_mask);
 120                         return 0;
 121                 }
 122         }
 123
 124         housekeeping_flags |= flags;
 125
 126         free_bootmem_cpumask_var(non_housekeeping_mask);
 127
 128         return 1;
 129 }
 130
 131 static int __init housekeeping_nohz_full_setup(char *str)
 132 {
 133         unsigned int flags;
 134
 135         flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
 136
 137         return housekeeping_setup(str, flags);
 138 }
 139 __setup("nohz_full=", housekeeping_nohz_full_setup);
 140
 141 static int __init housekeeping_isolcpus_setup(char *str)
 142 {
 143         unsigned int flags = 0;
 144
 145         while (isalpha(*str)) {
 146                 if (!strncmp(str, "nohz,", 5)) {
 147                         str += 5;
 148                         flags |= HK_FLAG_TICK;
 149                         continue;
 150                 }
 151
 152                 if (!strncmp(str, "domain,", 7)) {
 153                         str += 7;
 154                         flags |= HK_FLAG_DOMAIN;
 155                         continue;
 156                 }
 157
 158                 pr_warn("isolcpus: Error, unknown flag\n");
 159                 return 0;
 160         }
 161
 162         /* Default behaviour for isolcpus without flags */
 163         if (!flags)
 164                 flags |= HK_FLAG_DOMAIN;
 165
 166         return housekeeping_setup(str, flags);
 167 }
 168 __setup("isolcpus=", housekeeping_isolcpus_setup);