Hi Oleg,
On Thu, 28 Nov 2013 17:31:48 +0100, Oleg Nesterov wrote:
> On 11/28, Namhyung Kim wrote:
>>
>> I thought we need a fetch_param anyway if we will add support for
>> cross-fetch later. But I won't insist it strongly, I can delay it to
>> later work and make current code simpler if you want. :)
>
> OK, great,
So do you want me to change to make it simpler without a fetch_param?
>
>> >> static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs
>> >> *regs)
>> >> {
>> >> struct trace_uprobe *tu;
>> >> + struct uprobe_task *utask;
>> >> int ret = 0;
>> >>
>> >> tu = container_of(con, struct trace_uprobe, consumer);
>> >> tu->nhit++;
>> >>
>> >> + utask = current->utask;
>> >> + if (utask == NULL)
>> >> + return UPROBE_HANDLER_REMOVE;
>> >
>> > Hmm, why? The previous change ensures ->utask is not NULL? If we hit
>> > NULL we have a bug, we should not remove this uprobe.
>>
>> Yes, I just want to be defensive. :)
>>
>> So do you suggest to add BUG_ON()?
>
> We are going to crash with the same effect if it is NULL ;)
I see. I'll just get rid of the if (...) part.
>
>> And can I convert or remove a
>> similar check in uprobes.c:pre_ssout() too?
>
> Well, yes, we _can_ do this. But unless you have the strong opinion
> I'd suggest to not do this. At least right now.
>
> To remind, perhaps we can revert the previous patch later if we find
> a better solution (placeholder).
OK, I'll just leave it as is.
>
> And. Note that we will change this code in any case. I suggested to
> use ->vaddr to avoid the other (potentially conflicting) changes in
> uprobes.h. Even if we use current->utask, we should add another member
> into the union. But again, it would be better to do this later, and
> the change will be trivial.
Got it. Thank you for the explanation.
Thanks,
Namhyung
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