Commits
Yijing Wang committed 67546762978
PCI: Protect pci_bus->slots with pci_slot_mutex, not pci_bus_sem
Rajat Jain reported a deadlock when PCIe hot-add and AER recovery happen at
the same time:
thread 1:
pciehp_enable_slot
pciehp_configure_device
pci_bus_add_devices
pci_bus_add_device
device_attach
device_lock(dev) # acquire device lock
...
pciehp_probe
init_slot
pci_hp_register
pci_create_slot
down_write(pci_bus_sem) # deadlock here
thread 2:
aer_isr_one_error
aer_process_err_device
do_recovery
broadcast_error_message(..., report_error_detected)
pci_walk_bus(..., cb=report_error_detected, ...)
down_read(&pci_bus_sem) # acquire pci_bus_sem
report_error_detected(dev) # cb()
device_lock(dev) # deadlock here
Previously, the bus->devices and bus->slots list were protected by
pci_bus_sem. In pci_create_slot(), we held it for writing so we could
add to the bus->slots list.
Add a new local pci_slot_mutex to protect bus->slots. Hold pci_bus_sem for
reading while searching the bus->devices list.
[bhelgaas: changelog]
Link: http://lkml.kernel.org/r/CAA93t1qpPqbih+UB0McA_d_+2rVaNkXsinAUxYzK9+JXSS+L-g@mail.gmail.com
Reported-by: Rajat Jain <rajatja@google.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>