On 2018-07-03 14:04, Lukas Wunner wrote:
On Mon, Jul 02, 2018 at 06:52:47PM -0400, Sinan Kaya wrote:
If a bridge supports hotplug and observes a PCIe fatal error, the
following
events happen:
1. AER driver removes the devices from PCI tree on fatal error
2. AER driver brings down the link by issuing a secondary bus reset
waits
for the link to come up.
3. Hotplug driver observes a link down interrupt
4. Hotplug driver tries to remove the devices waiting for the rescan
lock
but devices are already removed by the AER driver and AER driver is
waiting
for the link to come back up.
5. AER driver tries to re-enumerate devices after polling for the link
state to go up.
6. Hotplug driver obtains the lock and tries to remove the devices
again.
If a bridge is a hotplug capable bridge, mask hotplug interrupts
before the
reset and unmask afterwards.
Would it work for you if you just amended the AER driver to skip
removal and re-enumeration of devices if the port is a hotplug bridge?
Just check for is_hotplug_bridge in struct pci_dev.
I tend to agree with you Lukas.
on this line I already have follow up patches
although I am waiting for Bjorn to review some patch-series before that.
[PATCH v2 0/6] Fix issues and cleanup for ERR_FATAL and ERR_NONFATAL
It doesn't look to me a an entirely a race condition since its guarded
by pci_lock_rescan_remove())
I observed that both hotplug and aer/dpc comes out of it in a quiet sane
state.
My thinking is: Disabling hotplug interrupts during ERR_FATAL,
is something little away from natural course of link_down event
handling, which is handled by pciehp more maturely.
so it would be just easy not to take any action e.g. removal and
re-enumeration of devices from ERR_FATAL handling point of view.
I leave it to Bjorn.
follwing is the patch wich I am trying to set it right and under test.
so till now I am in an opinion to handle this by checking in err.c
diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index 410c35c..607a234 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -292,15 +292,17 @@ void pcie_do_fatal_recovery(struct pci_dev *dev,
u32 service)
parent = udev->subordinate;
pci_lock_rescan_remove();
- list_for_each_entry_safe_reverse(pdev, temp, &parent->devices,
- bus_list) {
- pci_dev_get(pdev);
- pci_dev_set_disconnected(pdev, NULL);
- if (pci_has_subordinate(pdev))
- pci_walk_bus(pdev->subordinate,
- pci_dev_set_disconnected, NULL);
- pci_stop_and_remove_bus_device(pdev);
- pci_dev_put(pdev);
+ if (!udev->is_hotplug_bridge) {
+ list_for_each_entry_safe_reverse(pdev, temp,
&parent->devices,
+ bus_list) {
+ pci_dev_get(pdev);
+ pci_dev_set_disconnected(pdev, NULL);
+ if (pci_has_subordinate(pdev))
+ pci_walk_bus(pdev->subordinate,
+ pci_dev_set_disconnected,
NULL);
+ pci_stop_and_remove_bus_device(pdev);
+ pci_dev_put(pdev);
+ }
}
result = reset_link(udev, service);
@@ -318,7 +320,7 @@ void pcie_do_fatal_recovery(struct pci_dev *dev, u32
service)
}
if (result == PCI_ERS_RESULT_RECOVERED) {
- if (pcie_wait_for_link(udev, true))
+ if (pcie_wait_for_link(udev, true) &&
!udev->is_hotplug_bridge)
pci_rescan_bus(udev->bus);
pci_info(dev, "Device recovery from fatal error
successful\n");
dev->error_state = pci_channel_io_normal;
That would seem like a much simpler solution, given that it is known
that the link will flap on reset, causing the hotplug driver to remove
and re-enumerate devices. That would also cover cases where hotplug is
handled by a different driver than pciehp, or by the platform firmware.
Thanks,
Lukas
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