linux-kernel - Re: T400 suspend/resume regression -- bisected to a mystery merge commit

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Message-ID: <alpine.LFD.2.01.0910011817120.6996@localhost.localdomain>
Date:	Thu, 1 Oct 2009 18:21:50 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Theodore Tso <tytso@....edu>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	John Stultz <johnstul@...ibm.com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>, tglx@...utronix.de,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ondrej Zary <linux@...nbow-software.org>,
	Magnus Damm <magnus.damm@...il.com>
Subject: Re: T400 suspend/resume regression -- bisected to a mystery merge
 commit

On Thu, 1 Oct 2009, Theodore Tso wrote:
> 
> commit 8c3ee48dabee782d470cc4c7048ea64bb8b7d1cb
> Author: Theodore Ts'o <tytso@....edu>
> Date:   Thu Oct 1 20:39:03 2009 -0400
> 
>     Revert "timekeeping: Update clocksource with stop_machine"
>     
>     This reverts commit 75c5158f70c065b9704b924503d96e8297838f79.

Hmm. Looks good. But you didn't cc most of the people actually involved 
with that commit (Martin who is the author, and John who acked it).

I think the revert is the right thing to do, especially as that 
'clocksource_mutex' looks totally bogus. Either the thing is protected by 
'stop_machine' or it's not. In neither case does it seem to make any sense 
to replace a spinlock with a mutex. 

And resuming anything with a big mutex is crazy anyway. 

That said, I do wonder if this is already fixed. See commit 
89133f93508137231251543d1732da638e6022e1:

    clocksource: Resume clocksource without taking the clocksource mutex

which already undid the part that probably mattered for you. That said, I 
still do think that that mutex is dubious, so maybe we should undo it all.

		Linus
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