on 2010-2-22 20:06, Nick Piggin wrote:
>>>>> guarantee_online_cpus() truly does require callback_mutex, the
>>>>> cgroup_scan_tasks() iterator locking can protect changes in the cgroup
>>>>> hierarchy but it doesn't protect a store to cs->cpus_allowed or for
>>>>> hotplug.
>>>>
>>>> Right, but the callback_mutex was being removed by this patch.
>>>>
>>>
>>> I was making the case for it to be readded :)
>>
>> But cgroup_mutex is held when someone changes cs->cpus_allowed or doing hotplug,
>> so I think callback_mutex is not necessary in this case.
>
> So long as that's done consistently (and we should update the comments
> too).
I will update the comments.
>> ---
>> diff --git a/init/main.c b/init/main.c
>> index 4cb47a1..512ba15 100644
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -846,7 +846,7 @@ static int __init kernel_init(void * unused)
>> /*
>> * init can allocate pages on any node
>> */
>> - set_mems_allowed(node_possible_map);
>> + set_mems_allowed(node_states[N_HIGH_MEMORY]);
>> /*
>> * init can run on any cpu.
>> */
>> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
>> index ba401fa..e29b440 100644
>> --- a/kernel/cpuset.c
>> +++ b/kernel/cpuset.c
>> @@ -935,10 +935,12 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
>> struct task_struct *tsk = current;
>>
>> tsk->mems_allowed = *to;
>> + wmb();
>>
>> do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
>>
>> guarantee_online_mems(task_cs(tsk),&tsk->mems_allowed);
>> + wmb();
>> }
>>
>> /*
>
> You always need to comment barriers (and use smp_ variants unless you're
> doing mmio).
It's my mistake.
I'll remake a new patch and change it.
Thanks.
Miao
>
>
>> @@ -1391,11 +1393,10 @@ static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
>>
>> if (cs == &top_cpuset) {
>> cpumask_copy(cpus_attach, cpu_possible_mask);
>> - to = node_possible_map;
>> } else {
>> guarantee_online_cpus(cs, cpus_attach);
>> - guarantee_online_mems(cs, &to);
>> }
>> + guarantee_online_mems(cs, &to);
>>
>> /* do per-task migration stuff possibly for each in the threadgroup */
>> cpuset_attach_task(tsk, &to, cs);
>> @@ -2090,15 +2091,19 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
>> static int cpuset_track_online_nodes(struct notifier_block *self,
>> unsigned long action, void *arg)
>> {
>> + nodemask_t oldmems;
>> +
>> cgroup_lock();
>> switch (action) {
>> case MEM_ONLINE:
>> - case MEM_OFFLINE:
>> + oldmems = top_cpuset.mems_allowed;
>> mutex_lock(&callback_mutex);
>> top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
>> mutex_unlock(&callback_mutex);
>> - if (action == MEM_OFFLINE)
>> - scan_for_empty_cpusets(&top_cpuset);
>> + update_tasks_nodemask(&top_cpuset, &oldmems, NULL);
>> + break;
>> + case MEM_OFFLINE:
>> + scan_for_empty_cpusets(&top_cpuset);
>> break;
>> default:
>> break;
>> diff --git a/kernel/kthread.c b/kernel/kthread.c
>> index fbb6222..84c7f99 100644
>> --- a/kernel/kthread.c
>> +++ b/kernel/kthread.c
>> @@ -219,7 +219,7 @@ int kthreadd(void *unused)
>> set_task_comm(tsk, "kthreadd");
>> ignore_signals(tsk);
>> set_cpus_allowed_ptr(tsk, cpu_all_mask);
>> - set_mems_allowed(node_possible_map);
>> + set_mems_allowed(node_states[N_HIGH_MEMORY]);
>>
>> current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
>>
>
>
>
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