519cc8652b
When pciehp is converted to threaded IRQ handling, removal of unplugged
devices below a PCIe hotplug port happens synchronously in the IRQ thread.
Removal of devices typically entails a call to free_irq() by their drivers.
If those devices share their IRQ with the hotplug port, __free_irq()
deadlocks because it calls synchronize_irq() to wait for all hard IRQ
handlers as well as all threads sharing the IRQ to finish.
Actually it's sufficient to wait only for the IRQ thread of the removed
device, so call synchronize_hardirq() to wait for all hard IRQ handlers to
finish, but no longer for any threads. Compensate by rearranging the
control flow in irq_wait_for_interrupt() such that the device's thread is
allowed to run one last time after kthread_stop() has been called.
kthread_stop() blocks until the IRQ thread has completed. On completion
the IRQ thread clears its oneshot thread_mask bit. This is safe because
__free_irq() holds the request_mutex, thereby preventing __setup_irq() from
handing out the same oneshot thread_mask bit to a newly requested action.
Stack trace for posterity:
INFO: task irq/17-pciehp:94 blocked for more than 120 seconds.
schedule+0x28/0x80
synchronize_irq+0x6e/0xa0
__free_irq+0x15a/0x2b0
free_irq+0x33/0x70
pciehp_release_ctrl+0x98/0xb0
pcie_port_remove_service+0x2f/0x40
device_release_driver_internal+0x157/0x220
bus_remove_device+0xe2/0x150
device_del+0x124/0x340
device_unregister+0x16/0x60
remove_iter+0x1a/0x20
device_for_each_child+0x4b/0x90
pcie_port_device_remove+0x1e/0x30
pci_device_remove+0x36/0xb0
device_release_driver_internal+0x157/0x220
pci_stop_bus_device+0x7d/0xa0
pci_stop_bus_device+0x3d/0xa0
pci_stop_and_remove_bus_device+0xe/0x20
pciehp_unconfigure_device+0xb8/0x160
pciehp_disable_slot+0x84/0x130
pciehp_ist+0x158/0x190
irq_thread_fn+0x1b/0x50
irq_thread+0x143/0x1a0
kthread+0x111/0x130
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: linux-pci@vger.kernel.org
Link: https://lkml.kernel.org/r/d72b41309f077c8d3bee6cc08ad3662d50b5d22a.1529828292.git.lukas@wunner.de
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.