linux-kernel - 2.6.31 regression: system hang after pptp connection established

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Message-Id: <1253217553.3271.77.camel@tablet>
Date:	Thu, 17 Sep 2009 23:59:13 +0400
From:	Peter Volkov <pva@...too.org>
To:	gregkh@...e.de, torvalds@...ux-foundation.org
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: 2.6.31 regression: system hang after pptp connection established

Hi. 

After pptp connection is established my 2.6.31 system freezes while
2.6.30 works as expected. Bissecting gave me the following result:

commit ac89a9174decf343de049a06fad75681f71890eb
Author: Linus Torvalds <torvalds@...ux-foundation.org>
Date:   Sat Sep 5 13:27:10 2009 -0700

    pty: don't limit the writes to 'pty_space()' inside 'pty_write()'

and looks like reverting this patch from 2.6.31 fixes the problem.

Other observations: It's hard to say when exactly system hangs - it
hangs not immediatly, sometimes when I try to send some traffic,
sometimes when I switch ppp connection off. Hang is not complete: mouse
cursor keeps moving in Xorg, but every click gets no respond, I'm unable
to start new programs, in open xconsoles it's possible to input
something but after I press enter consoles hang too. Also there is no
way out of X (ctrl+alt+FN combo does not work) and connected to this
computer ssh consoles hang too (again, it's possible to put ls there but
after that it hangs). No new ssh connections possible due to time out.

In hope to get any oops I've started netconsole but at hang no new ouput
was there. I've managed to gather some information with SysRq (it's
gzipped in attachment) but I'm not sure how useful it is.

I've tried to establish pptp connection both over wireless and wired
connections and system hanged with both, so it looks like networking
drivers are not the reason here. BTW, I'm using networkmanager to
establish connection.

gzipped kernel config is in attachment.

Is this problem known? Does anybody experience same problem? Do you have
a fix? :)

-- 
Peter.

Download attachment "sysrq.txt.gz" of type "application/x-gzip" (10123 bytes)

Download attachment "config.gz" of type "application/x-gzip" (14771 bytes)