linux-kernel - Re: [Patch v2 20/22] x86/PCI: Refine the way to release PCI IRQ resources

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Message-ID: <20150128233834.GF17623@google.com>
Date:	Wed, 28 Jan 2015 17:38:34 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>, Lv Zheng <lv.zheng@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Len Brown <lenb@...nel.org>, Tony Luck <tony.luck@...el.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [Patch v2 20/22] x86/PCI: Refine the way to release PCI IRQ
 resources

On Wed, Jan 28, 2015 at 06:57:38PM +0800, Jiang Liu wrote:
> Some PCI device drivers assume that pci_dev->irq won't change after
> calling pci_disable_device() and pci_enable_device() during suspend and
> resume.
> 
> Commit c03b3b0738a56cf283b0d05256988d5e3c8bd719 ("x86, irq, mpparse:

Cosmetic: please use the conventional 12-char SHA1 as you did below.

> Release IOAPIC pin when PCI device is disabled") frees PCI IRQ
> resources when pci_disable_device() is called and reallocate IRQ
> resources when pci_enable_device() is called again. This breaks
> above assumption. So commit 3eec595235c1 ("x86, irq, PCI: Keep IRQ
> assignment for PCI devices during suspend/hibernation") and
> 9eabc99a635a ("x86, irq, PCI: Keep IRQ assignment for runtime power
> management") fix the issue by avoiding freeing/reallocating IRQ
> resources during PCI device suspend/resume. They achieve this by
> checking dev.power.is_prepared and dev.power.runtime_status.
> PM maintainer, Rafael, then pointed out that it's really an ugly fix
> which leaking PM internal state information to IRQ subsystem.
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