[PATCH] utrace_control: return -EINVAL for missing UTRACE_EVENT(QUIESCE)

[Oleg Nesterov]

On 08/18, Roland McGrath wrote:
>
> > Unfortunately, this doesn't help if a module doesn't use utrace_control()
> > but just returns UTRACE_SINGLESTEP/etc. Like Srikar's test-case does.
>
> Yes.  I thought about adding a WARN_ON or something.  But I think it would
> just wind up being confusing or overlooked.

Yes, agreed.

> > But I guess we can do nothing in this case, except perhaps we could add
> > pr_debug() into finish_callback(). I dunno. And in any case, the warning
> > from finish_callback() can't be always correct.
>
> I'm not sure what you mean here about "always correct".  It is always
> correct that you should not use UTRACE_SINGLESTEP without setting up a
> callback.

Yes. But finish_callback() can race with utrace_set_events() which can
clear QUIESCE after the callback returns UTRACE_SINGLESTEP, in this case
the warning is wrong.

Oleg.