netdev - Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred expansion/shrinking

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: <20150116213605.GE20315@casper.infradead.org>
Date:	Fri, 16 Jan 2015 21:36:05 +0000
From:	Thomas Graf <tgraf@...g.ch>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	David Laight <David.Laight@...LAB.COM>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"edumazet@...gle.com" <edumazet@...gle.com>,
	"john.r.fastabend@...el.com" <john.r.fastabend@...el.com>,
	"josh@...htriplett.org" <josh@...htriplett.org>,
	"netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org>
Subject: Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred
 expansion/shrinking

On 01/16/15 at 07:35pm, Patrick McHardy wrote:
> On 16.01, Thomas Graf wrote:
> > Right,but that's a Netlink dump issue and not specific to rhashtable.
> 
> Well, rhashtable (or generally resizing) will make it a lot worse.
> Usually we at worst miss entries which were added during the dump,
> which is made up by the notifications.
> 
> With resizing we might miss anything, its completely undeterministic.
> 
> > Putting the sequence number check in place should be sufficient
> > for sets, right?
> 
> I don't see how. The problem is that the ordering of the hash changes
> and it will skip different entries than those that have already been
> dumped.

Since an resize can only be triggered through insert/remove you
simply bump a sequence number when you insert/remove and have
userspace restart the dump when NLM_F_DUMP_INTR is set.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html