netdev - Re: [PATCH net] net/mlx4_en: mlx4_en_netpoll shouldn't call napi

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: <20140929.134704.646626597842088240.davem@davemloft.net>
Date:	Mon, 29 Sep 2014 13:47:04 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	amirv@...lanox.com
Cc:	idos@...lanox.com, netdev@...r.kernel.org, yevgenyp@...lanox.com,
	ogerlitz@...lanox.com
Subject: Re: [PATCH net] net/mlx4_en: mlx4_en_netpoll shouldn't call
 napi_schedule when port is down

From: Amir Vadai <amirv@...lanox.com>
Date: Mon, 29 Sep 2014 14:04:55 +0300

> From: Ido Shamay <idos@...lanox.com>
> 
> mlx4_en_netpoll, which is mlx4_en ndo_poll_controller callback,
> might be called when port is down, causing a napi_schedule when
> napi->poll callback in NULL. mutex_trylock is needed to acquire
> the port_state lock, since other threads may grab it and stop
> the port while we are in napi scheduling. Using trylock since in atomic
> context.
> 
> Signed-off-by: Ido Shamay <idos@...lanox.com>
> Signed-off-by: Amir Vadai <amirv@...lanox.com>

I don't think netpoll should 'variably succeed' on poll controller's
ability to immediately take a trylock.

You need to find a way to make this code always process the queues
when it is called, the approach you are taking here is not a correct.

If you've designed things in such a way that the locking here is
difficult, that's unfortunate but you still have to make this
function behave properly.
--
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