PCI: Fix pci_cfg_wait queue locking problem
[ Upstream commit 2a7e32d0547f41c5ce244f84cf5d6ca7fccee7eb ]
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, but cdcb33f98244
("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: cdcb33f98244 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
1 file changed