On 09/28/2013 03:33 PM, Linus Torvalds wrote:
On Sat, Sep 28, 2013 at 12:21 PM, Ingo Molnar<mi...@kernel.org> wrote:
If we do that then I suspect the next step will be queued rwlocks :-/ The
current rwlock_t implementation is rather primitive by modern standards.
(We'd probably have killed rwlock_t long ago if not for the
tasklist_lock.)
Yeah, I'm not happy about or rwlocks. That's one lock that currently
is so broken that I think we could easily argue for making that one
queued.
Waiman had a qrwlock series that looked reasonable, and I think his
later versions were drop-in replacements (ie they automatically just
did the RightThing(tm) wrt interrupts taking a recursive read lock - I
objected to the first versions that required that to be stated
explicitly).
The latest version (v3) will allow recursive read lock in interrupt
handlers.
I think Waiman's patches (even the later ones) made the queued rwlocks
be a side-by-side implementation with the old rwlocks, and I think
that was just being unnecessarily careful. It might be useful for
testing to have a config option to switch between the two, but we
might as well go all the way.
It is not actually a side-by-side implementation. A user can choose
either regular rwlock or the queue one, but never both by setting a
configuration parameter. However, I now think that maybe we should do it
the lockref way by pre-determining it on a per-architecture level
without user visible configuration option.
-Longman
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
