I think we have some issues with the e1000e usage of
pci_disable_link_state_locked(), which Yinghai added with 9f728f53dd70
("PCI/e1000e: Add and use pci_disable_link_state_locked()").
That fixed an AER deadlock in the following path, where pci_bus_sem is held
by pci_walk_bus(), and we deadlocked when we tried to re-acquire it in
pci_disable_link_state():
do_recovery
broadcast_error_message(..., report_slot_reset)
pci_walk_bus
down_read(&pci_bus_sem)
cb(...) # report_slot_reset
report_slot_reset
dev->driver->err_handler->slot_reset # e1000_io_slot_reset
e1000_io_slot_reset
e1000e_disable_aspm
pci_disable_link_state
down_read(&pci_bus_sem)
9f728f53dd70 fixed that by changing e1000e_disable_aspm() to use
pci_disable_link_state_locked() instead, which assumes pci_bus_sem is
already held.
That's fine for the e1000_io_slot_reset() path, where pci_bus_sem really
*is* held. But e1000e_disable_aspm() is also called from e1000_probe() and
__e1000_resume(), and in those paths, we *don't* hold pci_bus_sem.
In effect, the caller of pci_disable_link_state_locked() is promising that
pci_bus_sem is held, and __pci_disable_link_state() relies on that promise
for its locking. But e1000e isn't upholding its end of the bargain.
I'm not 100% sure __pci_disable_link_state() actually *needs* that locking:
it is only called from a driver, and it should be impossible for a device
or any upstream bridge to go away while a driver is bound to it. If
somebody wanted to analyze this further and propose a patch to remove the
locking (if it seems safe), that would be great.
But in any case, __pci_disable_link_state() should be able to rely on its
callers following the rules, so I'd like to see an e1000e change to use
pci_disable_link_state() from the paths where pci_bus_sem is not held.
Bjorn
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