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The pci_cfg_wait queue is used to prevent user-space config accesses to devices while they are recovering from reset. Previously we used these operations on pci_cfg_wait: __add_wait_queue(&pci_cfg_wait, ...) __remove_wait_queue(&pci_cfg_wait, ...) wake_up_all(&pci_cfg_wait) The wake_up acquires the wait queue lock, but the add and remove do not. Originally these were all protected by the pci_lock, butcdcb33f982("PCI: Avoid possible deadlock on pci_lock and p->pi_lock"), moved wake_up_all() outside pci_lock, so it could race with add/remove operations, which caused occasional kernel panics, e.g., during vfio-pci hotplug/unplug testing: Unable to handle kernel read from unreadable memory at virtual address ffff802dac469000 Resolve this by using wait_event() instead of __add_wait_queue() and __remove_wait_queue(). The wait queue lock is held by both wait_event() and wake_up_all(), so it provides mutual exclusion. Fixes:cdcb33f982("PCI: Avoid possible deadlock on pci_lock and p->pi_lock") Link: https://lore.kernel.org/linux-pci/79827f2f-9b43-4411-1376-b9063b67aee3@huawei.com/T/#u Based-on: https://lore.kernel.org/linux-pci/20191210031527.40136-1-zhengxiang9@huawei.com/ Based-on-patch-by: Xiang Zheng <zhengxiang9@huawei.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Tested-by: Xiang Zheng <zhengxiang9@huawei.com> Cc: Heyi Guo <guoheyi@huawei.com> Cc: Biaoxiang Ye <yebiaoxiang@huawei.com>
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.
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.