mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-02 02:46:43 +07:00
sched: Fix balance vs hotplug race
Since (e761b77: cpu hotplug, sched: Introduce cpu_active_map and redo
sched domain managment) we have cpu_active_mask which is suppose to rule
scheduler migration and load-balancing, except it never (fully) did.
The particular problem being solved here is a crash in try_to_wake_up()
where select_task_rq() ends up selecting an offline cpu because
select_task_rq_fair() trusts the sched_domain tree to reflect the
current state of affairs, similarly select_task_rq_rt() trusts the
root_domain.
However, the sched_domains are updated from CPU_DEAD, which is after the
cpu is taken offline and after stop_machine is done. Therefore it can
race perfectly well with code assuming the domains are right.
Cure this by building the domains from cpu_active_mask on
CPU_DOWN_PREPARE.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
Ingo Molnar
parent
e1b8090bdf
commit
6ad4c18884
@ -84,6 +84,7 @@ extern const struct cpumask *const cpu_active_mask;
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#define num_online_cpus() cpumask_weight(cpu_online_mask)
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#define num_possible_cpus() cpumask_weight(cpu_possible_mask)
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#define num_present_cpus() cpumask_weight(cpu_present_mask)
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#define num_active_cpus() cpumask_weight(cpu_active_mask)
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#define cpu_online(cpu) cpumask_test_cpu((cpu), cpu_online_mask)
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#define cpu_possible(cpu) cpumask_test_cpu((cpu), cpu_possible_mask)
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#define cpu_present(cpu) cpumask_test_cpu((cpu), cpu_present_mask)
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@ -92,6 +93,7 @@ extern const struct cpumask *const cpu_active_mask;
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#define num_online_cpus() 1
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#define num_possible_cpus() 1
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#define num_present_cpus() 1
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#define num_active_cpus() 1
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#define cpu_online(cpu) ((cpu) == 0)
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#define cpu_possible(cpu) ((cpu) == 0)
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#define cpu_present(cpu) ((cpu) == 0)
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18
kernel/cpu.c
18
kernel/cpu.c
@ -212,6 +212,8 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
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err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
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hcpu, -1, &nr_calls);
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if (err == NOTIFY_BAD) {
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set_cpu_active(cpu, true);
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nr_calls--;
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__raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
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hcpu, nr_calls, NULL);
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@ -223,11 +225,11 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
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/* Ensure that we are not runnable on dying cpu */
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cpumask_copy(old_allowed, ¤t->cpus_allowed);
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set_cpus_allowed_ptr(current,
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cpumask_of(cpumask_any_but(cpu_online_mask, cpu)));
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set_cpus_allowed_ptr(current, cpu_active_mask);
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err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
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if (err) {
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set_cpu_active(cpu, true);
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/* CPU didn't die: tell everyone. Can't complain. */
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if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
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hcpu) == NOTIFY_BAD)
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@ -292,9 +294,6 @@ int __ref cpu_down(unsigned int cpu)
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err = _cpu_down(cpu, 0);
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if (cpu_online(cpu))
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set_cpu_active(cpu, true);
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out:
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cpu_maps_update_done();
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stop_machine_destroy();
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@ -387,6 +386,15 @@ int disable_nonboot_cpus(void)
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* with the userspace trying to use the CPU hotplug at the same time
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*/
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cpumask_clear(frozen_cpus);
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for_each_online_cpu(cpu) {
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if (cpu == first_cpu)
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continue;
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set_cpu_active(cpu, false);
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}
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synchronize_sched();
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printk("Disabling non-boot CPUs ...\n");
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for_each_online_cpu(cpu) {
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if (cpu == first_cpu)
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@ -872,7 +872,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
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if (retval < 0)
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return retval;
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if (!cpumask_subset(trialcs->cpus_allowed, cpu_online_mask))
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if (!cpumask_subset(trialcs->cpus_allowed, cpu_active_mask))
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return -EINVAL;
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}
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retval = validate_change(cs, trialcs);
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@ -2010,7 +2010,7 @@ static void scan_for_empty_cpusets(struct cpuset *root)
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}
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/* Continue past cpusets with all cpus, mems online */
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if (cpumask_subset(cp->cpus_allowed, cpu_online_mask) &&
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if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) &&
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nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY]))
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continue;
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@ -2019,7 +2019,7 @@ static void scan_for_empty_cpusets(struct cpuset *root)
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/* Remove offline cpus and mems from this cpuset. */
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mutex_lock(&callback_mutex);
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cpumask_and(cp->cpus_allowed, cp->cpus_allowed,
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cpu_online_mask);
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cpu_active_mask);
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nodes_and(cp->mems_allowed, cp->mems_allowed,
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node_states[N_HIGH_MEMORY]);
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mutex_unlock(&callback_mutex);
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@ -2057,8 +2057,10 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
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switch (phase) {
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case CPU_ONLINE:
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case CPU_ONLINE_FROZEN:
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case CPU_DEAD:
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case CPU_DEAD_FROZEN:
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case CPU_DOWN_PREPARE:
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case CPU_DOWN_PREPARE_FROZEN:
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case CPU_DOWN_FAILED:
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case CPU_DOWN_FAILED_FROZEN:
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break;
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default:
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@ -2067,7 +2069,7 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
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cgroup_lock();
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mutex_lock(&callback_mutex);
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cpumask_copy(top_cpuset.cpus_allowed, cpu_online_mask);
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cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
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mutex_unlock(&callback_mutex);
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scan_for_empty_cpusets(&top_cpuset);
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ndoms = generate_sched_domains(&doms, &attr);
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@ -2114,7 +2116,7 @@ static int cpuset_track_online_nodes(struct notifier_block *self,
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void __init cpuset_init_smp(void)
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{
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cpumask_copy(top_cpuset.cpus_allowed, cpu_online_mask);
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cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
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top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
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hotcpu_notifier(cpuset_track_online_cpus, 0);
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@ -4134,7 +4134,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
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unsigned long flags;
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struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
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cpumask_copy(cpus, cpu_online_mask);
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cpumask_copy(cpus, cpu_active_mask);
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/*
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* When power savings policy is enabled for the parent domain, idle
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@ -4297,7 +4297,7 @@ load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
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int all_pinned = 0;
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struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
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cpumask_copy(cpus, cpu_online_mask);
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cpumask_copy(cpus, cpu_active_mask);
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/*
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* When power savings policy is enabled for the parent domain, idle
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@ -4694,7 +4694,7 @@ int select_nohz_load_balancer(int stop_tick)
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cpumask_set_cpu(cpu, nohz.cpu_mask);
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/* time for ilb owner also to sleep */
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if (cpumask_weight(nohz.cpu_mask) == num_online_cpus()) {
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if (cpumask_weight(nohz.cpu_mask) == num_active_cpus()) {
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if (atomic_read(&nohz.load_balancer) == cpu)
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atomic_set(&nohz.load_balancer, -1);
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return 0;
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@ -7093,7 +7093,7 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
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int ret = 0;
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rq = task_rq_lock(p, &flags);
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if (!cpumask_intersects(new_mask, cpu_online_mask)) {
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if (!cpumask_intersects(new_mask, cpu_active_mask)) {
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ret = -EINVAL;
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goto out;
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}
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@ -7115,7 +7115,7 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
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if (cpumask_test_cpu(task_cpu(p), new_mask))
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goto out;
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if (migrate_task(p, cpumask_any_and(cpu_online_mask, new_mask), &req)) {
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if (migrate_task(p, cpumask_any_and(cpu_active_mask, new_mask), &req)) {
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/* Need help from migration thread: drop lock and wait. */
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struct task_struct *mt = rq->migration_thread;
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@ -7269,19 +7269,19 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
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again:
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/* Look for allowed, online CPU in same node. */
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for_each_cpu_and(dest_cpu, nodemask, cpu_online_mask)
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for_each_cpu_and(dest_cpu, nodemask, cpu_active_mask)
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if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed))
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goto move;
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/* Any allowed, online CPU? */
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dest_cpu = cpumask_any_and(&p->cpus_allowed, cpu_online_mask);
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dest_cpu = cpumask_any_and(&p->cpus_allowed, cpu_active_mask);
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if (dest_cpu < nr_cpu_ids)
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goto move;
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/* No more Mr. Nice Guy. */
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if (dest_cpu >= nr_cpu_ids) {
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cpuset_cpus_allowed_locked(p, &p->cpus_allowed);
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dest_cpu = cpumask_any_and(cpu_online_mask, &p->cpus_allowed);
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dest_cpu = cpumask_any_and(cpu_active_mask, &p->cpus_allowed);
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/*
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* Don't tell them about moving exiting tasks or
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@ -7310,7 +7310,7 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
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*/
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static void migrate_nr_uninterruptible(struct rq *rq_src)
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{
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struct rq *rq_dest = cpu_rq(cpumask_any(cpu_online_mask));
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struct rq *rq_dest = cpu_rq(cpumask_any(cpu_active_mask));
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unsigned long flags;
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local_irq_save(flags);
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@ -7564,7 +7564,7 @@ static ctl_table *sd_alloc_ctl_cpu_table(int cpu)
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static struct ctl_table_header *sd_sysctl_header;
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static void register_sched_domain_sysctl(void)
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{
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int i, cpu_num = num_online_cpus();
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int i, cpu_num = num_possible_cpus();
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struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
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char buf[32];
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@ -7574,7 +7574,7 @@ static void register_sched_domain_sysctl(void)
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if (entry == NULL)
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return;
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for_each_online_cpu(i) {
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for_each_possible_cpu(i) {
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snprintf(buf, 32, "cpu%d", i);
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entry->procname = kstrdup(buf, GFP_KERNEL);
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entry->mode = 0555;
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@ -9100,7 +9100,7 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
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if (doms_new == NULL) {
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ndoms_cur = 0;
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doms_new = &fallback_doms;
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cpumask_andnot(doms_new[0], cpu_online_mask, cpu_isolated_map);
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cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
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WARN_ON_ONCE(dattr_new);
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}
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@ -9231,8 +9231,10 @@ static int update_sched_domains(struct notifier_block *nfb,
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switch (action) {
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case CPU_ONLINE:
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case CPU_ONLINE_FROZEN:
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case CPU_DEAD:
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case CPU_DEAD_FROZEN:
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case CPU_DOWN_PREPARE:
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case CPU_DOWN_PREPARE_FROZEN:
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case CPU_DOWN_FAILED:
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case CPU_DOWN_FAILED_FROZEN:
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partition_sched_domains(1, NULL, NULL);
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return NOTIFY_OK;
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@ -9279,7 +9281,7 @@ void __init sched_init_smp(void)
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#endif
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get_online_cpus();
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mutex_lock(&sched_domains_mutex);
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arch_init_sched_domains(cpu_online_mask);
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arch_init_sched_domains(cpu_active_mask);
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cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
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if (cpumask_empty(non_isolated_cpus))
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cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
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