linux-kernel - Re: [hrtimers] Re: Regression affecting b43 LP-PHY card

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Date:	Tue, 10 May 2011 12:06:41 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Rafał Miłecki <zajec5@...il.com>
Cc:	b43-dev <b43-dev@...ts.infradead.org>,
	linux-wireless@...r.kernel.org,
	Juan Carlos Romero <juancarlos.romero@...il.com>,
	Larry Finger <Larry.Finger@...inger.net>,
	Ben Greear <greearb@...delatech.com>,
	Jamie Lokier <jamie@...reable.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alexander Shishkin <virtuoso@...nd.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [hrtimers] Re: Regression affecting b43 LP-PHY card

On Tue, 2011-05-10 at 20:57 +0200, Rafał Miłecki wrote:
> W dniu 10 maja 2011 00:52 użytkownik Rafał Miłecki <zajec5@...il.com> napisał:
> > In this situation we decided to bisect. I was a little afraid of last
> > merges so we took older 2.6.38 as GOOD (we tested this twice) and
> > wireless-testing commit before my ssb changes as BAD. Today Juan
> > finished bisecting kernel:
> > http://pastebin.com/HSKbRzpB
> >
> > According to his bisection the first bad commit is
> > e06383db9ec591696a06654257474b85bac1f8cb [0]:
> > hrtimers: extend hrtimer base code to handle more then 2 clockids
> >
> > Does it make any sense to you? Could this be some timing issue?
> >
> > It was too late to test this today, we (Juan) will work on this
> > tomorrow. It's impossible to revert this commit from HEAD of
> > wireless-testing, so my idea is to checkout commit, test, revert,
> > test.
> >
> > Did anyone else experience any similar problems with latest wireless-testing?
> >
> >
> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e06383db9ec591696a06654257474b85bac1f8cb
> 
> Today Juan checkouted commit e06383db9ec591696a06654257474b85bac1f8cb
> and tested it. He was disconnected really soon.
> 
> Then he reverted e06383db9ec591696a06654257474b85bac1f8cb and tested
> again. Connection was stable, he downloaded 2GB file over network.
> 
> 
> John S.: your commit does not touch Broadcom card directly, but it
> seems it somehow affects it. I suspect there can be some timing issue.
> Do you have any idea what could it be, how can we debug this?

Sorry for the trouble!

My commit exposed a few spots where hrtimers were being initialized
before hrtimer_init is called, which caused problems. Thomas provided a
solution that makes such behavior still function ok:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=ce31332d3c77532d6ea97ddcb475a2b02dd358b4

Let me know if the issue is still reproducible with Linus' latest git
tree.

thanks
-john



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