On PREEMPT_RT, currently both aer_irq and aer_isr run in separate threads,
at the same FIFO priority. This can lead to the aer_isr thread starving
the aer_irq thread, particularly if multi_error_valid causes a scan of
all devices, and multiple errors are raised during the scan.
On !PREEMPT_RT, or if aer_irq runs at a higher priority than aer_isr, these
errors can be queued as single-error events as they happen. But if aer_irq
can't run until aer_isr finishes, by that time the multi event bit will be
set again, causing a new scan and an infinite loop.
Signed-off-by: Crystal Wood <crwood@xxxxxxxxxx>
---
I'm seeing this on a particular ARM server when using /sys/bus/pci/rescan,
though the internal reporter sometimes saw it happen on boot as well.
On !PREEMPT_RT, or with this patch, a finite number of errors are emitted
and the scan completes.
---
drivers/pci/pcie/aer.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index 15ed541d2fbe..6945a112a5cd 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -1671,7 +1671,8 @@ static int aer_probe(struct pcie_device *dev)
set_service_data(dev, rpc);
status = devm_request_threaded_irq(device, dev->irq, aer_irq, aer_isr,
- IRQF_SHARED, "aerdrv", dev);
+ IRQF_NO_THREAD | IRQF_SHARED,
+ "aerdrv", dev);
if (status) {
pci_err(port, "request AER IRQ %d failed\n", dev->irq);
return status;
--
2.47.1
