Oleg Nesterov <oleg@xxxxxxxxxx> writes:
> On 06/15, Greg Kurz wrote:
>>
>> @@ -176,6 +177,17 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
>> if (tracer)
>> tpid = task_pid_nr_ns(tracer, ns);
>> }
>> + actpid = 0;
>> + sighand = rcu_dereference(p->sighand);
>> + if (sighand) {
>> + struct pid_namespace *pid_ns;
>> + unsigned long flags;
>> + spin_lock_irqsave(&sighand->siglock, flags);
>
> Well. This is not exactly right. We have lock_task_sighand() for this.
>
> But. Why do you need ->siglock? Why rcu_read_lock() is not enough?
>
> Hmm. You don't even need pid_ns afaics, you could simply look at
> pid->numbers[pid->level].
I got this moving in that direction, but I admit I probably didn't look
close enough. I just remember it is always tricky when accessing a
process and dealing with races with things like unhash_process().
Eric
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