On Wed, Jul 04, 2018 at 10:46:41AM +0200, David Sterba wrote:
> On Tue, Jul 03, 2018 at 11:01:02AM +0100, Mark Rutland wrote:
> > In many cases, it would be useful to be able to use the full
> > sanity-checked refcount helpers regardless of CONFIG_REFCOUNT_FULL, as
> > this would help to avoid duplicate warnings where callers try to
> > sanity-check refcount manipulation.
> >
> > This patch refactors things such that the full refcount helpers were
> > always built, as refcount_${op}_checked(), such that they can be used
> > regardless of CONFIG_REFCOUNT_FULL. This will allow code which *always*
> > wants a checked refcount to opt-in, avoiding the need to duplicate the
> > logic for warnings.
> >
> > There should be no functional change as a result of this patch.
> >
> > Signed-off-by: Mark Rutland <[email protected]>
> > Cc: Boqun Feng <[email protected]>
> > Cc: David Sterba <[email protected]>
> > Cc: Ingo Molnar <[email protected]>
> > Cc: Kees Cook <[email protected]>
> > Cc: Peter Zijlstra <[email protected]>
> > Cc: Peter Zijlstra <[email protected]>
> > Cc: Will Deacon <[email protected]>
>
> I dare to give it my
>
> Reviewed-by: David Sterba <[email protected]>
Cheers!
> as my POC implementations were crap and Mark's version is much better.
Please don't think that your implementations were bad; I just already had an
idea as to what this could look like.
> > ---
> > include/linux/refcount.h | 27 +++++++++++++++++-------
> > lib/refcount.c | 53
> > +++++++++++++++++++++++-------------------------
> > 2 files changed, 45 insertions(+), 35 deletions(-)
> >
> > Dave pointed out that it would be useful to be able to opt-in to full checks
> > regardless of CONFIG_REFCOUNT_FULL, so that we can simplify callsites where
> > we
> > always want checks. I've spotted a few of these in code which is still
> > awaiting
> > conversion.
>
> The motivation was code like
>
> WARN_ON(refcount_read(&ref));
> if (refcount_dec_and_test(&ref)) { ... }
>
> so the warning is redundant for REFCOUNT_FULL, but I'm going to use the
> _checked versions everywhere the performance of refcounts is not
> critical.
If you will have conversion patches, do you want to pick this up as the start
of a series?
Thanks,
Mark.
