linux-kernel - Re: [PATCH] pci: fix kexec with power state D3

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Message-Id: <200903081133.33020.rjw@sisk.pl>
Date:	Sun, 8 Mar 2009 11:33:31 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Wilcox <matthew@....cx>,
	Jesse Brandeburg <jesse.brandeburg@...il.com>,
	David Miller <davem@...emloft.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	NetDev <netdev@...r.kernel.org>, linux-pci@...r.kernel.org,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH] pci: fix kexec with power state D3

On Sunday 08 March 2009, Rafael J. Wysocki wrote:
> On Sunday 08 March 2009, Ingo Molnar wrote:
> > 
> > * Rafael J. Wysocki <rjw@...k.pl> wrote:
> > 
> > > On Sunday 08 March 2009, Yinghai Lu wrote:
> > > > 
> > > > Impact: second kernel by kexec will have some pci devices working
> > > > 
> > > > Found one system with 82575EB, in the kernel that is kexeced, probe igb
> > > > failed with -2.
> > > > 
> > > > it looks like the same behavior happened on forcedeth.
> > > > try to check system_state to make sure if put it on D3
> > > 
> > > This is not enough, because the PM code doesn't change 
> > > system_state and it uses pci_set_power_state too.
> > > 
> > > > Jesse Brandeburg said that we should do that check in core 
> > > > code instead of every device driver.
> > > 
> > > Well, I'm not really sure.  The drivers are where the bug is.
> > 
> > So Yinghai has now written a driver fix and a generic code fix 
> > as well and both are being rejected pointing to the other side? 
> > 
> > This really sucks for users (who'd be happy with any of the 
> > patches) and the disagreement needs to be resolved ASAP.
> 
> I hope you read my other comment (that you deleted from the reply)?
> 
> If we're going to fix this at the core level along the Yinghai's patch lines,
> we'll have to introduce a few additional values for system_state and make
> suspend and hibernation code use them.
> 
> Do you think it's worth the effort, given that only a couple of drivers have
> been found to be affected so far?

And, quite frankly, I'm not sure if users will be happy with the $subject
patch, because it _really_ breaks things (well, the kexec users who don't use
suspend might be, but surely suspend users who don't use kexec won't).

Thanks,
Rafael
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