![Peter Xu](/assets/img/avatar_default.png)
The "isolcpus=" parameter allows sub-parameters before the cpulist is specified, and if the parser detects an unknown sub-parameters the whole parameter will be ignored. This design is incompatible with itself when new sub-parameters are added. An older kernel will not recognize the new sub-parameter and will invalidate the whole parameter so the CPU isolation will not take effect. It emits a warning: isolcpus: Error, unknown flag The better and compatible way is to allow "isolcpus=" to skip unknown sub-parameters, so that even if new sub-parameters are added an older kernel will still be able to behave as usual even if with the new sub-parameter specified on the command line. Ideally this should have been there when the first sub-parameter for "isolcpus=" was introduced. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20200403223517.406353-1-peterx@redhat.com
200 lines
5.2 KiB
C
200 lines
5.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Housekeeping management. Manage the targets for routine code that can run on
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* any CPU: unbound workqueues, timers, kthreads and any offloadable work.
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*
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* Copyright (C) 2017 Red Hat, Inc., Frederic Weisbecker
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* Copyright (C) 2017-2018 SUSE, Frederic Weisbecker
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*
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*/
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#include "sched.h"
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DEFINE_STATIC_KEY_FALSE(housekeeping_overridden);
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EXPORT_SYMBOL_GPL(housekeeping_overridden);
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static cpumask_var_t housekeeping_mask;
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static unsigned int housekeeping_flags;
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bool housekeeping_enabled(enum hk_flags flags)
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{
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return !!(housekeeping_flags & flags);
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}
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EXPORT_SYMBOL_GPL(housekeeping_enabled);
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int housekeeping_any_cpu(enum hk_flags flags)
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{
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int cpu;
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if (static_branch_unlikely(&housekeeping_overridden)) {
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if (housekeeping_flags & flags) {
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cpu = sched_numa_find_closest(housekeeping_mask, smp_processor_id());
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if (cpu < nr_cpu_ids)
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return cpu;
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return cpumask_any_and(housekeeping_mask, cpu_online_mask);
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}
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}
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return smp_processor_id();
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}
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EXPORT_SYMBOL_GPL(housekeeping_any_cpu);
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const struct cpumask *housekeeping_cpumask(enum hk_flags flags)
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{
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if (static_branch_unlikely(&housekeeping_overridden))
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if (housekeeping_flags & flags)
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return housekeeping_mask;
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return cpu_possible_mask;
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}
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EXPORT_SYMBOL_GPL(housekeeping_cpumask);
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void housekeeping_affine(struct task_struct *t, enum hk_flags flags)
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{
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if (static_branch_unlikely(&housekeeping_overridden))
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if (housekeeping_flags & flags)
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set_cpus_allowed_ptr(t, housekeeping_mask);
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}
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EXPORT_SYMBOL_GPL(housekeeping_affine);
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bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
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{
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if (static_branch_unlikely(&housekeeping_overridden))
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if (housekeeping_flags & flags)
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return cpumask_test_cpu(cpu, housekeeping_mask);
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return true;
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}
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EXPORT_SYMBOL_GPL(housekeeping_test_cpu);
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void __init housekeeping_init(void)
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{
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if (!housekeeping_flags)
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return;
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static_branch_enable(&housekeeping_overridden);
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if (housekeeping_flags & HK_FLAG_TICK)
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sched_tick_offload_init();
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/* We need at least one CPU to handle housekeeping work */
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WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
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}
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static int __init housekeeping_setup(char *str, enum hk_flags flags)
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{
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cpumask_var_t non_housekeeping_mask;
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cpumask_var_t tmp;
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int err;
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alloc_bootmem_cpumask_var(&non_housekeeping_mask);
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err = cpulist_parse(str, non_housekeeping_mask);
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if (err < 0 || cpumask_last(non_housekeeping_mask) >= nr_cpu_ids) {
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pr_warn("Housekeeping: nohz_full= or isolcpus= incorrect CPU range\n");
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free_bootmem_cpumask_var(non_housekeeping_mask);
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return 0;
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}
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alloc_bootmem_cpumask_var(&tmp);
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if (!housekeeping_flags) {
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alloc_bootmem_cpumask_var(&housekeeping_mask);
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cpumask_andnot(housekeeping_mask,
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cpu_possible_mask, non_housekeeping_mask);
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cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
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if (cpumask_empty(tmp)) {
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pr_warn("Housekeeping: must include one present CPU, "
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"using boot CPU:%d\n", smp_processor_id());
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__cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
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__cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
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}
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} else {
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cpumask_andnot(tmp, cpu_present_mask, non_housekeeping_mask);
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if (cpumask_empty(tmp))
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__cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
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cpumask_andnot(tmp, cpu_possible_mask, non_housekeeping_mask);
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if (!cpumask_equal(tmp, housekeeping_mask)) {
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pr_warn("Housekeeping: nohz_full= must match isolcpus=\n");
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free_bootmem_cpumask_var(tmp);
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free_bootmem_cpumask_var(non_housekeeping_mask);
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return 0;
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}
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}
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free_bootmem_cpumask_var(tmp);
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if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
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if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
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tick_nohz_full_setup(non_housekeeping_mask);
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} else {
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pr_warn("Housekeeping: nohz unsupported."
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" Build with CONFIG_NO_HZ_FULL\n");
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free_bootmem_cpumask_var(non_housekeeping_mask);
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return 0;
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}
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}
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housekeeping_flags |= flags;
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free_bootmem_cpumask_var(non_housekeeping_mask);
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return 1;
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}
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static int __init housekeeping_nohz_full_setup(char *str)
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{
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unsigned int flags;
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flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
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return housekeeping_setup(str, flags);
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}
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__setup("nohz_full=", housekeeping_nohz_full_setup);
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static int __init housekeeping_isolcpus_setup(char *str)
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{
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unsigned int flags = 0;
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bool illegal = false;
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char *par;
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int len;
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while (isalpha(*str)) {
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if (!strncmp(str, "nohz,", 5)) {
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str += 5;
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flags |= HK_FLAG_TICK;
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continue;
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}
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if (!strncmp(str, "domain,", 7)) {
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str += 7;
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flags |= HK_FLAG_DOMAIN;
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continue;
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}
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if (!strncmp(str, "managed_irq,", 12)) {
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str += 12;
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flags |= HK_FLAG_MANAGED_IRQ;
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continue;
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}
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/*
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* Skip unknown sub-parameter and validate that it is not
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* containing an invalid character.
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*/
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for (par = str, len = 0; *str && *str != ','; str++, len++) {
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if (!isalpha(*str) && *str != '_')
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illegal = true;
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}
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if (illegal) {
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pr_warn("isolcpus: Invalid flag %.*s\n", len, par);
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return 0;
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}
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pr_info("isolcpus: Skipped unknown flag %.*s\n", len, par);
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str++;
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}
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/* Default behaviour for isolcpus without flags */
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if (!flags)
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flags |= HK_FLAG_DOMAIN;
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return housekeeping_setup(str, flags);
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}
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__setup("isolcpus=", housekeeping_isolcpus_setup);
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