Oleg Nesterov <[email protected]> writes:
> On 04/10, Eric W. Biederman wrote:
>>
>> +int kthreadd(void *unused)
>> +{
>> + /* Setup a clean context for our children to inherit. */
>> + kthreadd_setup();
>> +
>> + current->flags |= PF_NOFREEZE;
>> +
>> + for (;;) {
>> + wait_event(kthread_create_work,
>> + !list_empty(&kthread_create_list));
>> +
>> + spin_lock(&kthread_create_lock);
>> + while (!list_empty(&kthread_create_list)) {
>
> Do we need to check the condition under lock? We can miss an event,
> but then it will be noticed by wait_event() above.
We need to be certain there is something on the list before we remove
it. Otherwise we will start dereferencing bad pointers.
> IOW,
>
> for (;;) {
> wait_event(kthread_create_work,
> !list_empty(&kthread_create_list));
>
> while (!list_empty(&kthread_create_list)) {
> struct kthread_create_info *create;
>
> spin_lock(&kthread_create_lock);
> create = list_entry(kthread_create_list.next,
> struct kthread_create_info, list);
> list_del_init(&create->list);
> spin_unlock(&kthread_create_lock);
>
> create_kthread(create);
> }
> }
I guess since we are the only process to ever remove things from the
list that would be safe.
Eric
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