netdev - Re: [BUG] net: cpu offline cause napi stall

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: <1306930399.3476.1.camel@edumazet-laptop>
Date:	Wed, 01 Jun 2011 14:13:19 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Frank Blaschka <blaschka@...ux.vnet.ibm.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-s390@...r.kernel.org, heiko.carstens@...ibm.com
Subject: Re: [BUG] net: cpu offline cause napi stall

Le mercredi 01 juin 2011 à 12:33 +0200, Frank Blaschka a écrit :
> Hi Dave, Eric,
> 
> during heavy network load we turn off/on cpus.
> Sometimes this causes a stall on the network device.
> Digging into the dump I found out following:
> 
> napi is scheduled but does not run. From the I/O buffers
> and the napi state I see napi/rx_softirq processing has stopped
> because the budget was reached. napi stays in the
> softnet_data poll_list and the rx_softirq was raised again.
> 
> I assume at this time the cpu offline comes in.
> the rx softirq is raised/moved to another cpu but napi stays in the poll_list
> of the softnet_data of the now offline cpu.
> 
> reviewing dev_cpu_callback (net/core/dev.c) I did not find the poll_list
> is transfered to the new cpu. Do you think this could cause the stall or
> did I miss something?
> 
> Thx for your help.

Hi Frank

I believe you are right, I cant see where the poll_list transfert from
dead cpu to online cpu is done.

Do you want to prepare a patch ?

Thanks !



--
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