>> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
>> index 1042b3c..032139d 100644
>> --- a/kernel/cgroup.c
>> +++ b/kernel/cgroup.c
>> @@ -2102,21 +2102,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
>> if (retval)
>> goto out_free_group_list;
>>
>> - /* prevent changes to the threadgroup list while we take a snapshot. */
>> - read_lock(&tasklist_lock);
>> - if (!thread_group_leader(leader)) {
>> - /*
>> - * a race with de_thread from another thread's exec() may strip
>> - * us of our leadership, making while_each_thread unsafe to use
>> - * on this task. if this happens, there is no choice but to
>> - * throw this task away and try again (from cgroup_procs_write);
>> - * this is "double-double-toil-and-trouble-check locking".
>> - */
>> - read_unlock(&tasklist_lock);
>> - retval = -EAGAIN;
>> - goto out_free_group_list;
>> - }
>> -
>> tsk = leader;
>> i = 0;
>> do {
>> @@ -2145,7 +2130,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
>> group_size = i;
>> tset.tc_array = group;
>> tset.tc_array_len = group_size;
>> - read_unlock(&tasklist_lock);
>
> You still need rcu_read_lock()/rcu_read_unlock() around
> do {
>
> } while_each_thread()
>
> because threadgroup_lock() doesn't lock the part that remove a thread from
> its group on exit.
>
and inside rcu critical section, you can't call kmalloc(GFP_KERNEL)!!
--
To unsubscribe from this list: send the line "unsubscribe cgroups" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
