Messages in this thread | | | Date | Fri, 26 Apr 2019 03:25:50 -0400 | From | "Boqun Feng" <> | Subject | Re: [PATCH 24/28] locking/lockdep: Remove !dir in lock irq usa ge check |
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On Fri, Apr 26, 2019, at 3:06 PM, Yuyang Du wrote: > Thanks for review. > > On Fri, 26 Apr 2019 at 04:03, Peter Zijlstra <peterz@infradead.org> wrote: > > > > On Wed, Apr 24, 2019 at 06:19:30PM +0800, Yuyang Du wrote: > > > In mark_lock_irq(), the following checks are performed: > > > > > > ---------------------------------- > > > | -> | unsafe | read unsafe | > > > |----------------------------------| > > > | safe | F B | F* B* | > > > |----------------------------------| > > > | read safe | F? B* | - | > > > ---------------------------------- > > > > > > Where: > > > F: check_usage_forwards > > > B: check_usage_backwards > > > *: check enabled by STRICT_READ_CHECKS > > > ?: check enabled by the !dir condition > > > > > > From checking point of view, the special F? case does not make sense, > > > whereas it perhaps is made for peroformance concern. As later patch will > > > address this issue, remove this exception, which makes the checks > > > consistent later. > > > > > > With STRICT_READ_CHECKS = 1 which is default, there is no functional > > > change. > > > > Oh man.. thinking required and it is way late.. anyway this whole read > > stuff made me remember we had a patch set on readlocks last year. > > > > https://lkml.kernel.org/r/20180411135110.9217-1-boqun.feng@gmail.com > > > > I remember reviewing that a few times and then it dropped on the floor, > > probably because Spectre crap or something sucked up all my time again :/ > > > > Sorry Boqun! >
That's all right. I was also too busy to send another spin...
> Oh man, I thought about the read-write lock stuff, but I didn't know > Boqun's patch. Let me hurt my brain looking at that patch. >
Yuyang, a few about the status, I've changed a little on the algorithm, the latest code is at
git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git arr-rfc-wip
but unfortunately, I haven't got time to rework the comments and documents, so be aware of this inconsistency.
Feel free to ask me any question, and I will try to send out a fresh spin in next month.
Regards, Boqun
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