Re: [PATCH] pci: lock the pci_cfg_wait queue for the consistency of data

From: Matthew Wilcox
Date: Mon Oct 28 2019 - 12:30:48 EST

On Mon, Oct 28, 2019 at 05:18:09PM +0800, Xiang Zheng wrote:
> Commit "7ea7e98fd8d0" suggests that the "pci_lock" is sufficient,
> and all the callers of pci_wait_cfg() are wrapped with the "pci_lock".
> However, since the commit "cdcb33f98244" merged, the accesses to
> the pci_cfg_wait queue are not safe anymore. A "pci_lock" is
> insufficient and we need to hold an additional queue lock while
> read/write the wait queue.
> So let's use the add_wait_queue()/remove_wait_queue() instead of
> __add_wait_queue()/__remove_wait_queue().

As I said earlier, this reintroduces the deadlock addressed by