linux-kernel - RE: [RFC][PATCH] pstore: Skip spinlock when just one cpu is online

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Message-ID: <A5ED84D3BB3A384992CBB9C77DEDA4D414A1DFC8@USINDEM103.corp.hds.com>
Date:	Mon, 10 Dec 2012 23:52:21 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Don Zickus <dzickus@...hat.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"cbouatmailru@...il.com" <cbouatmailru@...il.com>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: RE: [RFC][PATCH] pstore: Skip spinlock when just one cpu is online

> Now my first reaction would be, if that is the scenario, why couldn't cpuA release the lock within one second.  Because if cpuA is stuck
> talking with firmware, then your patch to force the unlock is probably going to trip over the same problems.
> (those problems include dealing with resetting a firmware state machine)
> 
> IOW, your patch is just one of many minefields you will have to cross in order to be successful.

I agree that I need to fix the platform driver's deadlocking as well to make an overall system workable. 
(I just wanted to fix the deadlocking problems step by step.)


> 
> Without any testing to show that you have cleared all those minefields, I am leaning against your patch for now.  I would rather have a
> complete patchset that fixes all the problems in this path.

Thanks. I will try to make the complete patchset.

> 
> If you did have to go this route, why not take the 'reason' variable and pass it to some function 'in_panic_path(reason)' that tells you if
> you are panicing or not.  Then you can change the 'if in_nmi()' to 'if in_nmi() || in_panic'.
> 
> The panic path already disables irqs for you, not sure you need to do it again.  Unless you have some other path you are trying to
> protect in mind.

Thank you for the suggestion.
I will update my patch in accordance with your comment if anyone else disagree that.

> 
> Cheers,
> Don
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