linux-kernel - Re: [PATCH] mm: use srcu for shrinkers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 17 Jun 2015 18:33:36 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: use srcu for shrinkers

On Wed, 2015-06-17 at 09:47 +0200, Michal Hocko wrote:
> On the other hand using srcu is a neat idea. Shrinkers only need the
> existence guarantee when racing with unregister. Register even shouldn't
> be that interesting because such a shrinker wouldn't have much to
> shrink anyway so we can safely miss it AFAIU. With the srcu read lock
> we can finally get rid of the try_lock. I do not think you need an
> ugly spin_is_locked as the replacement though. We have the existence
> guarantee and that should be sufficient.

So the reason for the spin_is_locked check was that I was concerned
about new reader(s) that come in while doing the registry. Currently
this is forbidden by the trylock and fake-ish retry. But yes, perhaps I
was being over safe and we shouldn't be blockling the reclaim simply
because a shrinker is registering. And it would be cleaner to get rid of
the whole retry idea and just use rcu guarantees.

This is probably a little late in the game to try to push for 4.2, so
I'll send a v2 with any other updates that might come up once the merge
window closes.

Thanks,
Davidlohr

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/