On Thu, 28 Sep 2017, Sinan Kaya wrote:
On 9/27/2017 5:42 PM, Govindarajulu Varadarajan wrote:
CPU0 CPU1
---------------------------------------------------------------------
__driver_attach()
device_lock(&dev->mutex) <--- device mutex lock here
driver_probe_device()
pci_enable_sriov()
pci_iov_add_virtfn()
pci_device_add()
aer_isr() <--- pci aer error
do_recovery()
broadcast_error_message()
pci_walk_bus()
down_read(&pci_bus_sem) <--- rd sem
How about releasing the device_lock here on CPU0?>
pci_device_add() is called by driver's pci probe function. device_lock(dev)
should be held before calling pci driver probe function.
or in other words keep device_lock as short as possible?
The problem is not the duration device_lock is held. It is the order two locks
are aquired. We cannot control or implement a restriction that during
device_lock() is held, driver probe should not call pci function which aquires
pci_bus_sem. And in case of pci aer, aer handler needs to call driver err_handler()
for which we need to hold device_lock() before calling err_handler(). In order
to find all the devices on a pci bus, we should hold pci_bus_sem to do
pci_walk_bus().
down_write(&pci_bus_sem) <-- stuck on wr sem
report_error_detected()
device_lock(&dev->mutex)<--- DEAD LOCK
