On Fri, Nov 09, 2012 at 05:26:53PM -0800, Kees Cook wrote:
[....]
> >> @@ -171,7 +171,13 @@ static size_t ramoops_write_kmsg_hdr(struct
> >> persistent_ram_zone *prz)
> >> struct timeval timestamp;
> >> size_t len;
> >>
> >> - do_gettimeofday(×tamp);
> >> + /* Handle dumping before timekeeping has resumed. */
> >> + if (unlikely(timekeeping_suspended)) {
> >> + timestamp.tv_sec = 0;
> >> + timestamp.tv_usec = 0;
> >> + } else
> >> + do_gettimeofday(×tamp);
> >> +
> >
> > Would nulling out the timestamp be better done in do_gettimeofday()? That
> > way we don't have to export timekeeping internals and users would get
> > something more sane for this corner case.
>
> Well... I'm not sure. If we don't want to expose the
> timekeeping_suspended variable, maybe we need a function to check
> this? I think it's probably better to find the users of timekeeping
> that could call it when suspended. That's why I figured the BUG was
> there. Very very few things should be attempting to call gettimeofday
> in a place where it might be suspended. As such, it seems like those
> things should be able to determine how to handle it. Maybe not
> everything would be sensible to get back 0s.
>
> In this particular case, I'm fine with removing the BUG and returning
> 0 instead, since that's fine for ramoops. :)
In the lack of agreement on kernel/time/timekeeping.c change, I can't
apply the patch. And personally I tend to agree that doing this workaround
in the pstore code is odd. How about introducing ___do_gettimeofday() that
is safe to call when suspened, and the func would have good kernel doc
comments explaining the purpose of it?
Thanks,
Anton.
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