linux-kernel - Re: Wireless IBSS on Linux-2.6.34 broken by commit 3bbb9ec946428b96657126768f65487a48dd090c

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Date:	Sun, 23 May 2010 11:49:26 +0200
From:	Johannes Berg <johannes.berg@...el.com>
To:	Jeff Chua <jeff.chua.linux@...il.com>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	"johnstul@...ibm.com" <johnstul@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Intel Linux Wireless <ilw@...ux.intel.com>,
	"John W. Linville" <linville@...driver.com>,
	Frans Pop <elendil@...net.nl>,
	"Chatre, Reinette" <reinette.chatre@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Wireless IBSS on Linux-2.6.34 broken by commit
 3bbb9ec946428b96657126768f65487a48dd090c

On Sun, 2010-05-23 at 05:58 +0100, Jeff Chua wrote:
> Wireless IBSS on Linux-2.6.34 is broken. Reverting commit
> 3bbb9ec946428b96657126768f65487a48dd090c makes it work again. This was
> tested by bisecting the kernel.
> 
> I'm using 6200 AGN ...
> 
> cfg80211: Calling CRDA to update world regulatory domain
> iwlagn: Intel(R) Wireless WiFi Link AGN driver for Linux, in-tree:
> iwlagn: Copyright(c) 2003-2010 Intel Corporation
> iwlagn 0000:02:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
> iwlagn 0000:02:00.0: setting latency timer to 64
> iwlagn 0000:02:00.0: Detected Intel(R) Centrino(R) Advanced-N 6200 AGN, REV=0x74
> iwlagn 0000:02:00.0: Tunable channels: 13 802.11bg, 24 802.11a channels
> iwlagn 0000:02:00.0: irq 46 for MSI/MSI-X
> iwlagn 0000:02:00.0: loaded firmware version 9.193.4.1 build 19710
> 
> 
> 
> So, where should the fix be?
> 
> 
> Here's the commit ...
> 
> 3bbb9ec946428b96657126768f65487a48dd090c is the first bad commit
> commit 3bbb9ec946428b96657126768f65487a48dd090c
> Author: Arjan van de Ven <arjan@...ux.intel.com>
> Date:   Thu Mar 11 14:04:36 2010 -0800
> 
>     timers: Introduce the concept of timer slack for legacy timers

This is odd -- as Arjan said more logging would be good, if you can
enable mac80211 IBSS debug (though in one case we had recently that
_fixed_ the issue unfortunately) -- it's under the mac80211 debug menu
Kconfig.

FWIW, I don't know about anything in mac80211 that would be timer
sensitive?

johannes

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