linux-kernel - Re: [rfc] "fair" rw spinlocks

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, 25 Nov 2009 07:54:12 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [rfc] "fair" rw spinlocks

On Tue, Nov 24, 2009 at 09:47:56PM +0100, Andi Kleen wrote:
> Nick Piggin <npiggin@...e.de> writes:
> 
> > Hi,
> >
> > Last time this issue came up that I could see, I don't think
> > there were objections to making rwlocks fair, the main
> > difficulty seemed to be that we allow reentrant read locks
> > (so a write lock waiting must not block arbitrary read lockers).
> >
> > Nowadays our rwlock usage is smaller although still quite a
> > few, so it would make better sense to do a conversion by
> > introducing a new lock type and move them over I guess.
> 
> You want to do a new lock type for potentially nested rwlocks?
> 
> >From the basic idea it sounds good, but according
> to grep the current tree has hundreds of rwlocks all over,
> and how would you reliably detect whether they are nestable
> or not?
> 
> I assume it's not something that could be easily analyzed
> at compile time and relying on runtime would seem dangerous.
> 
> Basically it sounds like quite a lot of work.
> 
> A better plan might be to have new types which are non nestable
> and only move over audited code to fair rwlocks.

No that's what I meant, the new type would be non nestable.


--
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/