From: Florian Westphal <fw@strlen.de>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Florian Westphal <fw@strlen.de>,
netfilter-devel <netfilter-devel@vger.kernel.org>
Subject: Re: [PATCH 3/3] netfilter: ctnetlink: allow userspace to set labels
Date: Tue, 27 Nov 2012 14:09:04 +0100 [thread overview]
Message-ID: <20121127130904.GB14156@breakpoint.cc> (raw)
In-Reply-To: <20121127123149.GA2351@1984>
Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > > For the update case, I think we'll have to iterate over the mask and
> > > use xchg to update words, thus, we avoid any interference ongoing bit
> > > testing.
> >
> > Could you elaborate?
> > Why is memcpy not good enough here?
>
> while updating the connlabel via memcpy, some test_bit on the
> connlabel may be already happening. I was suggesting some way to avoid
> racing with it.
I don't understand why its racing.
Is there a case where we update a word, and test_bit can return
"bit is set", even if the bit in the word is neither currently
set nor about to be set?
If not, then I don't see the race; either the test happens
before we copied the word, or afterwards; regardless of copy vs.
xchg?
next prev parent reply other threads:[~2012-11-27 13:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-15 15:55 [PATCH 0/3] netfilter: add connlabel conntrack extension Florian Westphal
2012-11-15 15:55 ` [PATCH 1/3] " Florian Westphal
2012-11-15 15:55 ` [PATCH 2/3] netfilter: ctnetlink: deliver labels to userspace via CTA_LABELS attribute Florian Westphal
2012-11-15 15:55 ` [PATCH 3/3] netfilter: ctnetlink: allow userspace to set labels Florian Westphal
2012-11-27 11:18 ` Pablo Neira Ayuso
2012-11-27 11:50 ` Florian Westphal
2012-11-27 12:31 ` Pablo Neira Ayuso
2012-11-27 13:09 ` Florian Westphal [this message]
2012-11-27 14:13 ` Pablo Neira Ayuso
2012-11-27 14:24 ` Florian Westphal
2012-11-30 13:58 ` Pablo Neira Ayuso
2012-11-30 14:02 ` Florian Westphal
2012-11-30 18:34 ` Pablo Neira Ayuso
2012-11-30 21:36 ` Florian Westphal
2012-12-03 11:04 ` Pablo Neira Ayuso
2012-12-03 11:13 ` Florian Westphal
2012-12-03 12:58 ` Pablo Neira Ayuso
2012-11-27 12:39 ` Pablo Neira Ayuso
2012-11-16 10:02 ` [PATCH 0/3] netfilter: add connlabel conntrack extension Pablo Neira Ayuso
2012-11-16 11:31 ` Florian Westphal
2012-11-16 11:52 ` Pablo Neira Ayuso
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