Messages in this thread Patch in this message | | | From | Xiang Zheng <> | Subject | [PATCH v3] PCI: Lock the pci_cfg_wait queue for the consistency of data | Date | Tue, 10 Dec 2019 11:15:27 +0800 |
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7ea7e98fd8d0 ("PCI: Block on access to temporarily unavailable pci device") 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 ("PCI: Avoid possible deadlock on pci_lock and p->pi_lock") merged, the accesses to the pci_cfg_wait queue are not safe anymore. This would cause kernel panic in a very low chance (See more detailed information from the below link). 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(). Also move the wait queue functionality around the "schedule()" function to avoid reintroducing the deadlock addressed by "cdcb33f98244".
Signed-off-by: Xiang Zheng <zhengxiang9@huawei.com> Cc: Heyi Guo <guoheyi@huawei.com> Cc: Biaoxiang Ye <yebiaoxiang@huawei.com> Link: https://lore.kernel.org/linux-pci/79827f2f-9b43-4411-1376-b9063b67aee3@huawei.com/ ---
v3: Improve the commit subject and message.
v2: Move the wait queue functionality around the "schedule()".
--- drivers/pci/access.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/access.c b/drivers/pci/access.c index 2fccb5762c76..09342a74e5ea 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -207,14 +207,14 @@ static noinline void pci_wait_cfg(struct pci_dev *dev) { DECLARE_WAITQUEUE(wait, current); - __add_wait_queue(&pci_cfg_wait, &wait); do { set_current_state(TASK_UNINTERRUPTIBLE); raw_spin_unlock_irq(&pci_lock); + add_wait_queue(&pci_cfg_wait, &wait); schedule(); + remove_wait_queue(&pci_cfg_wait, &wait); raw_spin_lock_irq(&pci_lock); } while (dev->block_cfg_access); - __remove_wait_queue(&pci_cfg_wait, &wait); } /* Returns 0 on success, negative values indicate error. */ -- 2.19.1
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