Date: Tue, 23 Apr 2013 11:09:16 GMT From: Jukka Ukkonen <jau@oxit.fi> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/178079: Switching TCP CC algorithm panics on sparc64 with a complaint from the MMU Message-ID: <201304231109.r3NB9GgZ064621@red.freebsd.org> Resent-Message-ID: <201304231110.r3NBA2ck085398@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
>Number: 178079 >Category: kern >Synopsis: Switching TCP CC algorithm panics on sparc64 with a complaint from the MMU >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Tue Apr 23 11:10:01 UTC 2013 >Closed-Date: >Last-Modified: >Originator: Jukka Ukkonen >Release: 9.1-STABLE >Organization: ----- >Environment: FreeBSD mimir 9.1-STABLE FreeBSD 9.1-STABLE #0 r249763M: Tue Apr 23 05:47:38 EEST 2013 root@mimir:/usr/obj/usr/src/sys/GENERIC sparc64 >Description: An attempt to switch the TCP congestion control algorithm on a sparc64 system causes an instant panic. The message shown on the console mentions something about NewReno and then something about the MMU. Though I do not have the exact text shown to quote here, it looked to me quite a lot like one of those MMU complaints one gets for improperly aligned data. Notice: I have never seen anything remotely similar happening on an amd64. So, it is supposedly impossible to replicate the problem using a CPU which does not care about the data alignment. >How-To-Repeat: On a sparc64 system follow these steps: First make sure you have the alternate CC modules loaded... kldload /boot/kernel/cc_*.ko Then try this... sysctl net.inet.tcp.cc.algorithm=htcp At least in my case this has been a guaranteed trick to panic the system with a complaint from the MMU. >Fix: Not the foggiest idea yet. I will keep a crash dump around for a while just in case someone wishes to have a chance to see it. I cannot promise to save it for very long, though. OTOH with the consistency I have been getting new crash dumps when touching the CC algorithm on sparc64 it should be easy enough for anyone to generate ones own crash dump if needs be. ;-) >Release-Note: >Audit-Trail: >Unformatted:
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201304231109.r3NB9GgZ064621>