linux-kernel - Re: [PATCH 8/9] PCI / ACPI / PM: Platform support for PCI PME wake-up (rev. 7)

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Date:	Fri, 12 Feb 2010 17:27:11 -0800
From:	Gary Hade <garyhade@...ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Gary Hade <garyhade@...ibm.com>,
	linux-pm@...ts.linux-foundation.org,
	Linux PCI <linux-pci@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Moore, Robert" <robert.moore@...el.com>,
	Matthew Garrett <mjg@...hat.com>,
	Bjorn Helgaas <bjorn.helgaas@...com>
Subject: Re: [PATCH 8/9] PCI / ACPI / PM: Platform support for PCI PME
	wake-up (rev. 7)

On Sat, Feb 13, 2010 at 01:20:29AM +0100, Rafael J. Wysocki wrote:
> On Friday 12 February 2010, Rafael J. Wysocki wrote:
> > On Friday 12 February 2010, Gary Hade wrote:
> ... 
> > > There seems to be a problem.
> > > 
> > > The first time I booted I was able to successfully hot-remove
> > > a PCIe card and then successfully hot-add it to a different slot.
> > > When I tried to hot-remove a PCI-X card that was also present
> > > during boot I saw that lingering blinking amber LED issue.
> > > 
> > > After rebooting I tried the same thing but this time I did
> > > not see the lingering blinking amber LED after removing the
> > > PCI-X card but I did see it when removing the PCIe card.
> > > I then tried to hot-add the PCIe card to a different slot
> > > and noticed the below messages.
> > > 
> > > I don't think I will be able to try to characterize this
> > > better or test any more patches until Monday.  
> > 
> > OK, thanks for testing.
> > 
> > It seems we have a deadlock on pci_acpi_notify_mtx, but I'm yet to understand
> > the exact mechanism of it.
> 
> In fact there are two problems in there.  First, the bridge event notification
> calls handle_bridge_insertion() which attempts to install a PM notifier for
> the bridge and that deadlocks, because it tries to acquire the mutex
> recursively.  Second, apparently, init_bridge_misc() may be called in the
> notification code path and it attempts to unregister the notifier and register
> it again, which can't be done with pci_acpi_notify_mtx held.
> 
> I guess there are similar problems on the hot remove notification path.
> 
> Anyway, I have a new version of the patch and I'm going to test it a bit
> over the weekend.  Unfortunately, I don't have hardware with PCI hotplug
> capability, so I'll send you the new patch for testing on Monday, if you don't
> mind.

I don't mind.  Although I am concerned that my acpiphp only
testing on our IBM System x boxes may not be sufficient to
assure that PCI hotplug will work well on other PCI hotplug
capable systems.  I hope that others will also do some early
testing of this code.

Gary

-- 
Gary Hade
System x Enablement
IBM Linux Technology Center
503-578-4503  IBM T/L: 775-4503
garyhade@...ibm.com
http://www.ibm.com/linux/ltc

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