From: Bjorn Helgaas <[email protected]> [ Upstream commit cdcb33f9824429a926b971bf041a6cec238f91ff ]
pci_lock is an IRQ-safe spinlock that protects all accesses to PCI configuration space (see PCI_OP_READ() and PCI_OP_WRITE() in pci/access.c). The pci_cfg_access_unlock() path acquires pci_lock, then p->pi_lock (inside wake_up_all()). According to lockdep, there is a possible path involving snbep_uncore_pci_read_counter() that could acquire them in the reverse order: acquiring p->pi_lock, then pci_lock, which could result in a deadlock. Lockdep details are in the bugzilla below. Avoid the possible deadlock by dropping pci_lock before waking up any config access waiters. Link: https://bugzilla.kernel.org/show_bug.cgi?id=192901 Signed-off-by: Bjorn Helgaas <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- drivers/pci/access.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/pci/access.c b/drivers/pci/access.c index d11cdbb8fba3..7b5cf6d1181a 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -672,8 +672,9 @@ void pci_cfg_access_unlock(struct pci_dev *dev) WARN_ON(!dev->block_cfg_access); dev->block_cfg_access = 0; - wake_up_all(&pci_cfg_wait); raw_spin_unlock_irqrestore(&pci_lock, flags); + + wake_up_all(&pci_cfg_wait); } EXPORT_SYMBOL_GPL(pci_cfg_access_unlock); -- 2.11.0
