[PATCH 2/3] PCI: designware: Take lock when ACKing an interrupt

[Marc Zyngier <marc.zyngier@arm.com>]

Bizarrely, there is no lock taken in the irq_ack helper. This
puts the ack callback provided by a specific platform in a awkward
situation where there is no synchronization that would be expected
on other callback.

Introduce the required lock, giving some level of uniformity among
callbacks.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 drivers/pci/controller/dwc/pcie-designware-host.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index c3aa8b5fb51d..0a76948ed49e 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -202,11 +202,16 @@ static void dw_pci_bottom_ack(struct irq_data *d)
 {
 	struct msi_desc *msi = irq_data_get_msi_desc(d);
 	struct pcie_port *pp;
+	unsigned long flags;
 
 	pp = msi_desc_to_pci_sysdata(msi);
 
+	raw_spin_lock_irqsave(&pp->lock, flags);
+
 	if (pp->ops->msi_irq_ack)
 		pp->ops->msi_irq_ack(d->hwirq, pp);
+
+	raw_spin_unlock_irqrestore(&pp->lock, flags);
 }
 
 static struct irq_chip dw_pci_msi_bottom_irq_chip = {
-- 
2.19.1