linux-kernel - Aw: Re: stmmac ethernet in kernel 4.9-rc6: coalescing related pauses.

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]

Date:   Fri, 2 Dec 2016 15:05:21 +0100
From:   "Lino Sanfilippo" <LinoSanfilippo@....de>
To:     "Pavel Machek" <pavel@....cz>
Cc:     "Giuseppe CAVALLARO" <peppe.cavallaro@...com>,
        alexandre.torgue@...com, "David Miller" <davem@...emloft.net>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Aw: Re: stmmac ethernet in kernel 4.9-rc6: coalescing related
 pauses.

Hi,

> 
> There's nothing that protect stmmac_poll() from running concurently
> with stmmac_dma_interrupt(), right?
> 

could it be that there is also another issue concerned locking?:
The tx completion handler takes the xmit_lock in case that the
netif_queue is stopped. This is AFAICS unnecessary, since both
xmit and completion handler are already synchronized by the private
tx lock. But it is IMHO also dangerous:

In the xmit handler we have the locking order
1. xmit_lock
2. private tx lock

while in the completion handler its the reverse:

1. private tx lock
2. xmit lock.

Do I miss something?

Regards,
Lino