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sched: adjust when cpu_active and cpuset configurations are updated during cpu on/offlining

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Currently, when a cpu goes down, cpu_active is cleared before
CPU_DOWN_PREPARE starts and cpuset configuration is updated from a
default priority cpu notifier.  When a cpu is coming up, it's set
before CPU_ONLINE but cpuset configuration again is updated from the
same cpu notifier.

For cpu notifiers, this presents an inconsistent state.  Threads which
a CPU_DOWN_PREPARE notifier expects to be bound to the CPU can be
migrated to other cpus because the cpu is no more inactive.

Fix it by updating cpu_active in the highest priority cpu notifier and
cpuset configuration in the second highest when a cpu is coming up.
Down path is updated similarly.  This guarantees that all other cpu
notifiers see consistent cpu_active and cpuset configuration.

cpuset_track_online_cpus() notifier is converted to
cpuset_update_active_cpus() which just updates the configuration and
now called from cpuset_cpu_[in]active() notifiers registered from
sched_init_smp().  If cpuset is disabled, cpuset_update_active_cpus()
degenerates into partition_sched_domains() making separate notifier
for !CONFIG_CPUSETS unnecessary.

This problem is triggered by cmwq.  During CPU_DOWN_PREPARE, hotplug
callback creates a kthread and kthread_bind()s it to the target cpu,
and the thread is expected to run on that cpu.

* Ingo's test discovered __cpuinit/exit markups were incorrect.
  Fixed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Menage <menage@google.com>
This commit is contained in:
Tejun Heo 2010-06-08 21:40:36 +02:00
parent 50a323b730
commit 3a101d0548
5 changed files with 75 additions and 43 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
include/linux/cpu.h
View file

@ -52,6 +52,22 @@ struct notifier_block;
* CPU notifier priorities.
*/
enum {
/*
* SCHED_ACTIVE marks a cpu which is coming up active during
* CPU_ONLINE and CPU_DOWN_FAILED and must be the first
* notifier. CPUSET_ACTIVE adjusts cpuset according to
* cpu_active mask right after SCHED_ACTIVE. During
* CPU_DOWN_PREPARE, SCHED_INACTIVE and CPUSET_INACTIVE are
* ordered in the similar way.
*
* This ordering guarantees consistent cpu_active mask and
* migration behavior to all cpu notifiers.
*/
CPU_PRI_SCHED_ACTIVE = INT_MAX,
CPU_PRI_CPUSET_ACTIVE = INT_MAX - 1,
CPU_PRI_SCHED_INACTIVE = INT_MIN + 1,
CPU_PRI_CPUSET_INACTIVE = INT_MIN,
/* migration should happen before other stuff but after perf */
CPU_PRI_PERF = 20,
CPU_PRI_MIGRATION = 10,

6
include/linux/cpuset.h
View file

@ -20,6 +20,7 @@ extern int number_of_cpusets; /* How many cpusets are defined in system? */
extern int cpuset_init(void);
extern void cpuset_init_smp(void);
extern void cpuset_update_active_cpus(void);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
extern int cpuset_cpus_allowed_fallback(struct task_struct *p);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@ -132,6 +133,11 @@ static inline void set_mems_allowed(nodemask_t nodemask)
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
static inline void cpuset_update_active_cpus(void)
{
partition_sched_domains(1, NULL, NULL);
}
static inline void cpuset_cpus_allowed(struct task_struct *p,
struct cpumask *mask)
{

6
kernel/cpu.c
View file

@ -235,11 +235,8 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
return -EINVAL;
cpu_hotplug_begin();
set_cpu_active(cpu, false);
err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
if (err) {
set_cpu_active(cpu, true);
nr_calls--;
__cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
printk("%s: attempt to take down CPU %u failed\n",
@ -249,7 +246,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
if (err) {
set_cpu_active(cpu, true);
/* CPU didn't die: tell everyone. Can't complain. */
cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
@ -321,8 +317,6 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
goto out_notify;
BUG_ON(!cpu_online(cpu));
set_cpu_active(cpu, true);
/* Now call notifier in preparation. */
cpu_notify(CPU_ONLINE | mod, hcpu);

21
kernel/cpuset.c
View file

@ -2113,31 +2113,17 @@ static void scan_for_empty_cpusets(struct cpuset *root)
* but making no active use of cpusets.
*
* This routine ensures that top_cpuset.cpus_allowed tracks
* cpu_online_map on each CPU hotplug (cpuhp) event.
* cpu_active_mask on each CPU hotplug (cpuhp) event.
*
* Called within get_online_cpus(). Needs to call cgroup_lock()
* before calling generate_sched_domains().
*/
static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
unsigned long phase, void *unused_cpu)
void __cpuexit cpuset_update_active_cpus(void)
{
struct sched_domain_attr *attr;
cpumask_var_t *doms;
int ndoms;
switch (phase) {
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
case CPU_DOWN_FAILED:
case CPU_DOWN_FAILED_FROZEN:
break;
default:
return NOTIFY_DONE;
}
cgroup_lock();
mutex_lock(&callback_mutex);
cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
@ -2148,8 +2134,6 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
/* Have scheduler rebuild the domains */
partition_sched_domains(ndoms, doms, attr);
return NOTIFY_OK;
}
#ifdef CONFIG_MEMORY_HOTPLUG
@ -2203,7 +2187,6 @@ void __init cpuset_init_smp(void)
cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
hotcpu_notifier(cpuset_track_online_cpus, 0);
hotplug_memory_notifier(cpuset_track_online_nodes, 10);
cpuset_wq = create_singlethread_workqueue("cpuset");

69
kernel/sched.c
View file

@ -5804,17 +5804,46 @@ static struct notifier_block __cpuinitdata migration_notifier = {
.priority = CPU_PRI_MIGRATION,
};
static int __cpuinit sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
set_cpu_active((long)hcpu, true);
return NOTIFY_OK;
default:
return NOTIFY_DONE;
}
}
static int __cpuinit sched_cpu_inactive(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
set_cpu_active((long)hcpu, false);
return NOTIFY_OK;
default:
return NOTIFY_DONE;
}
}
static int __init migration_init(void)
{
void *cpu = (void *)(long)smp_processor_id();
int err;
/* Start one for the boot CPU: */
/* Initialize migration for the boot CPU */
err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
BUG_ON(err == NOTIFY_BAD);
migration_call(&migration_notifier, CPU_ONLINE, cpu);
register_cpu_notifier(&migration_notifier);
/* Register cpu active notifiers */
cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
return 0;
}
early_initcall(migration_init);
@ -7273,29 +7302,35 @@ int __init sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
}
#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
#ifndef CONFIG_CPUSETS
/*
* Add online and remove offline CPUs from the scheduler domains.
* When cpusets are enabled they take over this function.
* Update cpusets according to cpu_active mask. If cpusets are
* disabled, cpuset_update_active_cpus() becomes a simple wrapper
* around partition_sched_domains().
*/
static int update_sched_domains(struct notifier_block *nfb,
unsigned long action, void *hcpu)
static int __cpuexit cpuset_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action) {
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
case CPU_DOWN_FAILED:
case CPU_DOWN_FAILED_FROZEN:
partition_sched_domains(1, NULL, NULL);
cpuset_update_active_cpus();
return NOTIFY_OK;
default:
return NOTIFY_DONE;
}
}
static int __cpuexit cpuset_cpu_inactive(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
cpuset_update_active_cpus();
return NOTIFY_OK;
default:
return NOTIFY_DONE;
}
}
#endif
static int update_runtime(struct notifier_block *nfb,
unsigned long action, void *hcpu)
@ -7341,10 +7376,8 @@ void __init sched_init_smp(void)
mutex_unlock(&sched_domains_mutex);
put_online_cpus();
#ifndef CONFIG_CPUSETS
/* XXX: Theoretical race here - CPU may be hotplugged now */
hotcpu_notifier(update_sched_domains, 0);
#endif
hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
/* RT runtime code needs to handle some hotplug events */
hotcpu_notifier(update_runtime, 0);