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The revert of991de2e590("PCI, x86: Implement pcibios_alloc_irq() and pcibios_free_irq()") causes a problem for IOAPIC hotplug. The problem is that IRQs are allocated and freed in pci_enable_device() and pci_disable_device(). But there are some drivers which don't call pci_disable_device(), and they have good reasons not calling it, so if they're using IOAPIC their IRQs won't have a chance to be released from the IOAPIC. When this happens IOAPIC hot-removal fails with a kernel stack dump and an error message like this: [149335.697989] pin16 on IOAPIC2 is still in use. It turns out that we can fix it in a different way without moving IRQ allocation into pcibios_alloc_irq(), thus avoiding the regression of991de2e590. We can keep the allocation and freeing of IRQs as is within pci_enable_device()/pci_disable_device(), without breaking any previous assumption of the rest of the system, keeping compatibility with both the legacy and the modern drivers. We can accomplish this by implementing the existing __weak hook of pcibios_release_device() thus when a pci device is about to be deleted we get notified in the hook and take the chance to release its IRQ, if any, from the IOAPIC. Implement pcibios_release_device() for x86 to release any IRQ not released by the driver. Signed-off-by: Rui Wang <rui.y.wang@intel.com> Cc: tony.luck@intel.com Cc: linux-pci@vger.kernel.org Cc: rjw@rjwysocki.net Cc: linux-acpi@vger.kernel.org Cc: fengguang.wu@intel.com Cc: helgaas@kernel.org Cc: kbuild-all@01.org Cc: bhelgaas@google.com Link: http://lkml.kernel.org/r/1488288869-31290-2-git-send-email-rui.y.wang@intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.