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PCI: Protect pci_bus->slots with pci_slot_mutex, not pci_bus_sem

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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>
This commit is contained in:
Yijing Wang
2015-07-17 17:16:31 +08:00
committed by Bjorn Helgaas
parent ac10836b68
commit 6754676297
2 changed files with 13 additions and 8 deletions
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3
include/linux/pci.h
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@@ -446,7 +446,8 @@ struct pci_bus {
struct list_head children; /* list of child buses */
struct list_head devices; /* list of devices on this bus */
struct pci_dev *self; /* bridge device as seen by parent */
struct list_head slots; /* list of slots on this bus */
struct list_head slots; /* list of slots on this bus;
protected by pci_slot_mutex */
struct resource *resource[PCI_BRIDGE_RESOURCE_NUM];
struct list_head resources; /* address space routed to this bus */
struct resource busn_res; /* bus numbers routed to this bus */