diff options
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 213 |
1 files changed, 161 insertions, 52 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 88a7ede322bd..a86972a91991 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -592,7 +592,10 @@ static void lockdep_release_cpus_lock(void) void __weak arch_smt_update(void) { } #ifdef CONFIG_HOTPLUG_SMT + enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED; +static unsigned int cpu_smt_max_threads __ro_after_init; +unsigned int cpu_smt_num_threads __read_mostly = UINT_MAX; void __init cpu_smt_disable(bool force) { @@ -606,16 +609,33 @@ void __init cpu_smt_disable(bool force) pr_info("SMT: disabled\n"); cpu_smt_control = CPU_SMT_DISABLED; } + cpu_smt_num_threads = 1; } /* * The decision whether SMT is supported can only be done after the full * CPU identification. Called from architecture code. */ -void __init cpu_smt_check_topology(void) +void __init cpu_smt_set_num_threads(unsigned int num_threads, + unsigned int max_threads) { - if (!topology_smt_supported()) + WARN_ON(!num_threads || (num_threads > max_threads)); + + if (max_threads == 1) cpu_smt_control = CPU_SMT_NOT_SUPPORTED; + + cpu_smt_max_threads = max_threads; + + /* + * If SMT has been disabled via the kernel command line or SMT is + * not supported, set cpu_smt_num_threads to 1 for consistency. + * If enabled, take the architecture requested number of threads + * to bring up into account. + */ + if (cpu_smt_control != CPU_SMT_ENABLED) + cpu_smt_num_threads = 1; + else if (num_threads < cpu_smt_num_threads) + cpu_smt_num_threads = num_threads; } static int __init smt_cmdline_disable(char *str) @@ -625,9 +645,31 @@ static int __init smt_cmdline_disable(char *str) } early_param("nosmt", smt_cmdline_disable); -static inline bool cpu_smt_allowed(unsigned int cpu) +/* + * For Archicture supporting partial SMT states check if the thread is allowed. + * Otherwise this has already been checked through cpu_smt_max_threads when + * setting the SMT level. + */ +static inline bool cpu_smt_thread_allowed(unsigned int cpu) { - if (cpu_smt_control == CPU_SMT_ENABLED) +#ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC + return topology_smt_thread_allowed(cpu); +#else + return true; +#endif +} + +static inline bool cpu_bootable(unsigned int cpu) +{ + if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu)) + return true; + + /* All CPUs are bootable if controls are not configured */ + if (cpu_smt_control == CPU_SMT_NOT_IMPLEMENTED) + return true; + + /* All CPUs are bootable if CPU is not SMT capable */ + if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED) return true; if (topology_is_primary_thread(cpu)) @@ -642,7 +684,7 @@ static inline bool cpu_smt_allowed(unsigned int cpu) return !cpumask_test_cpu(cpu, &cpus_booted_once_mask); } -/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */ +/* Returns true if SMT is supported and not forcefully (irreversibly) disabled */ bool cpu_smt_possible(void) { return cpu_smt_control != CPU_SMT_FORCE_DISABLED && @@ -650,22 +692,8 @@ bool cpu_smt_possible(void) } EXPORT_SYMBOL_GPL(cpu_smt_possible); -static inline bool cpuhp_smt_aware(void) -{ - return topology_smt_supported(); -} - -static inline const struct cpumask *cpuhp_get_primary_thread_mask(void) -{ - return cpu_primary_thread_mask; -} #else -static inline bool cpu_smt_allowed(unsigned int cpu) { return true; } -static inline bool cpuhp_smt_aware(void) { return false; } -static inline const struct cpumask *cpuhp_get_primary_thread_mask(void) -{ - return cpu_present_mask; -} +static inline bool cpu_bootable(unsigned int cpu) { return true; } #endif static inline enum cpuhp_state @@ -768,10 +796,10 @@ static int bringup_wait_for_ap_online(unsigned int cpu) * SMT soft disabling on X86 requires to bring the CPU out of the * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The * CPU marked itself as booted_once in notify_cpu_starting() so the - * cpu_smt_allowed() check will now return false if this is not the + * cpu_bootable() check will now return false if this is not the * primary sibling. */ - if (!cpu_smt_allowed(cpu)) + if (!cpu_bootable(cpu)) return -ECANCELED; return 0; } @@ -1352,7 +1380,14 @@ static int takedown_cpu(unsigned int cpu) cpuhp_bp_sync_dead(cpu); tick_cleanup_dead_cpu(cpu); + + /* + * Callbacks must be re-integrated right away to the RCU state machine. + * Otherwise an RCU callback could block a further teardown function + * waiting for its completion. + */ rcutree_migrate_callbacks(cpu); + return 0; } @@ -1368,10 +1403,10 @@ void cpuhp_report_idle_dead(void) struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); BUG_ON(st->state != CPUHP_AP_OFFLINE); - rcu_report_dead(smp_processor_id()); + rcutree_report_cpu_dead(); st->state = CPUHP_AP_IDLE_DEAD; /* - * We cannot call complete after rcu_report_dead() so we delegate it + * We cannot call complete after rcutree_report_cpu_dead() so we delegate it * to an online cpu. */ smp_call_function_single(cpumask_first(cpu_online_mask), @@ -1467,8 +1502,22 @@ out: return ret; } +struct cpu_down_work { + unsigned int cpu; + enum cpuhp_state target; +}; + +static long __cpu_down_maps_locked(void *arg) +{ + struct cpu_down_work *work = arg; + + return _cpu_down(work->cpu, 0, work->target); +} + static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) { + struct cpu_down_work work = { .cpu = cpu, .target = target, }; + /* * If the platform does not support hotplug, report it explicitly to * differentiate it from a transient offlining failure. @@ -1477,7 +1526,18 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) return -EOPNOTSUPP; if (cpu_hotplug_disabled) return -EBUSY; - return _cpu_down(cpu, 0, target); + + /* + * Ensure that the control task does not run on the to be offlined + * CPU to prevent a deadlock against cfs_b->period_timer. + * Also keep at least one housekeeping cpu onlined to avoid generating + * an empty sched_domain span. + */ + for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)) { + if (cpu != work.cpu) + return work_on_cpu(cpu, __cpu_down_maps_locked, &work); + } + return -EBUSY; } static int cpu_down(unsigned int cpu, enum cpuhp_state target) @@ -1575,7 +1635,7 @@ void notify_cpu_starting(unsigned int cpu) struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE); - rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */ + rcutree_report_cpu_starting(cpu); /* Enables RCU usage on this CPU. */ cpumask_set_cpu(cpu, &cpus_booted_once_mask); /* @@ -1683,9 +1743,6 @@ static int cpu_up(unsigned int cpu, enum cpuhp_state target) if (!cpu_possible(cpu)) { pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n", cpu); -#if defined(CONFIG_IA64) - pr_err("please check additional_cpus= boot parameter\n"); -#endif return -EINVAL; } @@ -1699,7 +1756,7 @@ static int cpu_up(unsigned int cpu, enum cpuhp_state target) err = -EBUSY; goto out; } - if (!cpu_smt_allowed(cpu)) { + if (!cpu_bootable(cpu)) { err = -EPERM; goto out; } @@ -1793,6 +1850,16 @@ static int __init parallel_bringup_parse_param(char *arg) } early_param("cpuhp.parallel", parallel_bringup_parse_param); +static inline bool cpuhp_smt_aware(void) +{ + return cpu_smt_max_threads > 1; +} + +static inline const struct cpumask *cpuhp_get_primary_thread_mask(void) +{ + return cpu_primary_thread_mask; +} + /* * On architectures which have enabled parallel bringup this invokes all BP * prepare states for each of the to be onlined APs first. The last state @@ -2046,7 +2113,7 @@ static struct cpuhp_step cpuhp_hp_states[] = { [CPUHP_HRTIMERS_PREPARE] = { .name = "hrtimers:prepare", .startup.single = hrtimers_prepare_cpu, - .teardown.single = hrtimers_dead_cpu, + .teardown.single = NULL, }, [CPUHP_SMPCFD_PREPARE] = { .name = "smpcfd:prepare", @@ -2138,6 +2205,12 @@ static struct cpuhp_step cpuhp_hp_states[] = { .startup.single = NULL, .teardown.single = smpcfd_dying_cpu, }, + [CPUHP_AP_HRTIMERS_DYING] = { + .name = "hrtimers:dying", + .startup.single = NULL, + .teardown.single = hrtimers_cpu_dying, + }, + /* Entry state on starting. Interrupts enabled from here on. Transient * state for synchronsization */ [CPUHP_AP_ONLINE] = { @@ -2626,6 +2699,12 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) for_each_online_cpu(cpu) { if (topology_is_primary_thread(cpu)) continue; + /* + * Disable can be called with CPU_SMT_ENABLED when changing + * from a higher to lower number of SMT threads per core. + */ + if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu)) + continue; ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE); if (ret) break; @@ -2660,6 +2739,8 @@ int cpuhp_smt_enable(void) /* Skip online CPUs and CPUs on offline nodes */ if (cpu_online(cpu) || !node_online(cpu_to_node(cpu))) continue; + if (!cpu_smt_thread_allowed(cpu)) + continue; ret = _cpu_up(cpu, 0, CPUHP_ONLINE); if (ret) break; @@ -2838,20 +2919,19 @@ static const struct attribute_group cpuhp_cpu_root_attr_group = { #ifdef CONFIG_HOTPLUG_SMT +static bool cpu_smt_num_threads_valid(unsigned int threads) +{ + if (IS_ENABLED(CONFIG_SMT_NUM_THREADS_DYNAMIC)) + return threads >= 1 && threads <= cpu_smt_max_threads; + return threads == 1 || threads == cpu_smt_max_threads; +} + static ssize_t __store_smt_control(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { - int ctrlval, ret; - - if (sysfs_streq(buf, "on")) - ctrlval = CPU_SMT_ENABLED; - else if (sysfs_streq(buf, "off")) - ctrlval = CPU_SMT_DISABLED; - else if (sysfs_streq(buf, "forceoff")) - ctrlval = CPU_SMT_FORCE_DISABLED; - else - return -EINVAL; + int ctrlval, ret, num_threads, orig_threads; + bool force_off; if (cpu_smt_control == CPU_SMT_FORCE_DISABLED) return -EPERM; @@ -2859,21 +2939,39 @@ __store_smt_control(struct device *dev, struct device_attribute *attr, if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED) return -ENODEV; + if (sysfs_streq(buf, "on")) { + ctrlval = CPU_SMT_ENABLED; + num_threads = cpu_smt_max_threads; + } else if (sysfs_streq(buf, "off")) { + ctrlval = CPU_SMT_DISABLED; + num_threads = 1; + } else if (sysfs_streq(buf, "forceoff")) { + ctrlval = CPU_SMT_FORCE_DISABLED; + num_threads = 1; + } else if (kstrtoint(buf, 10, &num_threads) == 0) { + if (num_threads == 1) + ctrlval = CPU_SMT_DISABLED; + else if (cpu_smt_num_threads_valid(num_threads)) + ctrlval = CPU_SMT_ENABLED; + else + return -EINVAL; + } else { + return -EINVAL; + } + ret = lock_device_hotplug_sysfs(); if (ret) return ret; - if (ctrlval != cpu_smt_control) { - switch (ctrlval) { - case CPU_SMT_ENABLED: - ret = cpuhp_smt_enable(); - break; - case CPU_SMT_DISABLED: - case CPU_SMT_FORCE_DISABLED: - ret = cpuhp_smt_disable(ctrlval); - break; - } - } + orig_threads = cpu_smt_num_threads; + cpu_smt_num_threads = num_threads; + + force_off = ctrlval != cpu_smt_control && ctrlval == CPU_SMT_FORCE_DISABLED; + + if (num_threads > orig_threads) + ret = cpuhp_smt_enable(); + else if (num_threads < orig_threads || force_off) + ret = cpuhp_smt_disable(ctrlval); unlock_device_hotplug(); return ret ? ret : count; @@ -2901,6 +2999,17 @@ static ssize_t control_show(struct device *dev, { const char *state = smt_states[cpu_smt_control]; +#ifdef CONFIG_HOTPLUG_SMT + /* + * If SMT is enabled but not all threads are enabled then show the + * number of threads. If all threads are enabled show "on". Otherwise + * show the state name. + */ + if (cpu_smt_control == CPU_SMT_ENABLED && + cpu_smt_num_threads != cpu_smt_max_threads) + return sysfs_emit(buf, "%d\n", cpu_smt_num_threads); +#endif + return snprintf(buf, PAGE_SIZE - 2, "%s\n", state); } |