netdev - RE: [PATCH net-next 3/3] packet: use percpu mmap tx frame pending refcount

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: <063D6719AE5E284EB5DD2968C1650D6D459065@AcuExch.aculab.com>
Date:	Mon, 13 Jan 2014 11:58:30 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Daniel Borkmann' <dborkman@...hat.com>,
	Cong Wang <cwang@...pensource.com>
CC:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next 3/3] packet: use percpu mmap tx frame pending
 refcount

From: Daniel Borkmann
...
> But I think I found a different problem with this idea. It could
> happen with net devices as well, but probably less likely as there
> might be a better distribution of hold/puts among CPUs. However,
> for TX_RING, if we pin the process to a particular CPU, and since
> the destructor is invoked through ksoftirqd, we could end up with
> a misbalance and if the process runs long enough eventually
> overflow for one particular CPU. We could work around that, but I
> think it's not worth the effort.

The sum will be 'correct' when summed across all the cpu even if
one of the values has wrapped - provided all the arithmetic is
unsigned and the variables all the same type.

	David



--
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