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32a8cef274
Besides the IRQ thread, there are several other places in the driver which enable or disable the slot: - pciehp_probe() enables the slot if it's occupied and the pciehp_force module parameter is used. - pciehp_resume() enables or disables the slot after system sleep. - pciehp_queue_pushbutton_work() enables or disables the slot after the 5 second delay following an Attention Button press. - pciehp_sysfs_enable_slot() and pciehp_sysfs_disable_slot() enable or disable the slot on sysfs write. This requires locking and complicates pciehp's state machine. A simplification can be achieved by enabling and disabling the slot exclusively from the IRQ thread. Amend the functions listed above to request slot enable/disablement from the IRQ thread by either synthesizing a Presence Detect Changed event or, in the case of a disable user request (via sysfs or an Attention Button press), submitting a newly introduced force disable request. The latter is needed because the slot shall be forced off despite being occupied. For this force disable request, avoid colliding with Slot Status register bits by using a bit number greater than 16. For synchronous execution of requests (on sysfs write), wait for the request to finish and retrieve the result. There can only ever be one sysfs write in flight due to the locking in kernfs_fop_write(), hence there is no risk of returning the result of a different sysfs request to user space. The POWERON_STATE and POWEROFF_STATE is now no longer entered by the above-listed functions, but solely by the IRQ thread when it begins a power transition. Afterwards, it moves to STATIC_STATE. The same applies to canceling the Attention Button work, it likewise becomes an IRQ thread only operation. An immediate consequence is that the POWERON_STATE and POWEROFF_STATE is never observed by the IRQ thread itself, only by functions called in a different context, such as pciehp_sysfs_enable_slot(). So remove handling of these states from pciehp_handle_button_press() and pciehp_handle_link_change() which are exclusively called from the IRQ thread. Signed-off-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> |
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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.