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Subject[PATCH 0/4] pci aer: fix deadlock in do_recovery
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I am seeing a dead lock while loading enic driver with sriov enabled.

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
down_write(&pci_bus_sem) <-- stuck on wr sem
report_error_detected()
device_lock(&dev->mutex)<--- DEAD LOCK

This can also happen when aer error occurs while pci_dev->sriov_config() is
called.

Only fix I could think of is to lock &pci_bus_sem and try locking all
device->mutex under that pci_bus. If it fails, unlock all device->mutex
and &pci_bus_sem and try again. This approach seems to be hackish and I
do not have better solution. I would like to open the discussion for
this.

Path 1 and 2 are code refactoring for pci locking api. Patch 3 fixes the
issue.

With current fix, we hold mutex lock of parent device and all the
devices under the bus. This can exceed the size of held_locks in lockdep
if number of devices (VFs) exceed 48. Patch 4 extends this 63, max
supported by lockdep.

Govindarajulu Varadarajan (4):
pci: introduce __pci_walk_bus for caller with pci_bus_sem held
pci: code refactor pci_bus_lock/unlock/trylock
pci aer: fix deadlock in do_recovery
lockdep: make MAX_LOCK_DEPTH configurable from Kconfig

drivers/pci/bus.c | 13 ++++++++--
drivers/pci/pci.c | 38 ++++++++++++++++++++---------
drivers/pci/pcie/aer/aerdrv_core.c | 50 ++++++++++++++++++++++++++++++--------
fs/configfs/inode.c | 2 +-
include/linux/pci.h | 18 ++++++++++++++
include/linux/sched.h | 3 +--
kernel/locking/lockdep.c | 13 +++++-----
lib/Kconfig.debug | 10 ++++++++
8 files changed, 115 insertions(+), 32 deletions(-)

--
2.14.1

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