linux-kernel - Re: 2.6.29 -mm merge plans

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]

Message-ID: <20090107014915.GE3390@wotan.suse.de>
Date:	Wed, 7 Jan 2009 02:49:15 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.29 -mm merge plans

On Wed, Jan 07, 2009 at 02:38:45AM +0100, Andi Kleen wrote:
> Nick Piggin <npiggin@...e.de> writes:
> >
> > I can't see a problem with putting a global mutex around sys_sync (almost
> > by definition, any app in the last 10+ years that calls sys_sync is not
> > performance critical).
> 
> Hmm, but sync() used to (is still?) livelocky and when it takes a

It's not livelocky because it no longer has to do repeated passes
over the superblock list. It is subject to the single inode syncing
issue where it can get stuck behind a process dirtying memory (same
as fsync) but we've decided not to add complexity to improve that
just yet, and see whether it turns out to be a real problem.

> minute or so to flush (and I've seen that) do you really want any
> other sync user to block for a minute too?

sys_sync B which is invoked *after* sys_sync caller A should not
return before A. If you didn't have a global lock, they'd tend to
block one another's pages anyway. I think it's OK.

--
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/