Hi, We met a deadlock triggered by a NONFATAL AER event during a sysfs
"sriov_numvfs" operation. Any suggestion to fix such deadlock ?

  enable one VF
  # echo 1 > /sys/devices/pci0000:74/0000:74:00.0/0000:75:00.0/sriov_numvfs

  The sysfs "sriov_numvfs" side is:

    sriov_numvfs_store
      device_lock                               # hold the device_lock
        ...
        pci_enable_sriov
          sriov_enable
            ...
            pci_device_add
              down_write(&pci_bus_sem) 	        # wait for up_read(&pci_bus_sem)

  The AER side is:

    pcie_do_recovery
      pci_walk_bus
        down_read(&pci_bus_sem)                 # hold the rw_semaphore
        report_resume
          device_lock                           # wait for device_unlock()

The calltrace is as below:

[  258.411464] INFO: task kworker/0:1:13 blocked for more than 120 seconds.
[  258.418139]       Tainted: G         C O      5.1.0-rc1-ge2e3ca0 #1
[  258.424379] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  258.432172] kworker/0:1     D    0    13      2 0x00000028
[  258.437640] Workqueue: events aer_recover_work_func
[  258.442496] Call trace:
[  258.444933]  __switch_to+0xb4/0x1b8
[  258.448409]  __schedule+0x1ec/0x720
[  258.451884]  schedule+0x38/0x90
[  258.455012]  schedule_preempt_disabled+0x20/0x38
[  258.459610]  __mutex_lock.isra.1+0x150/0x518
[  258.463861]  __mutex_lock_slowpath+0x10/0x18
[  258.468112]  mutex_lock+0x34/0x40
[  258.471413]  report_resume+0x1c/0x78
[  258.474973]  pci_walk_bus+0x58/0xb0
[  258.478451]  pcie_do_recovery+0x18c/0x248
[  258.482445]  aer_recover_work_func+0xe0/0x118
[  258.486783]  process_one_work+0x1e4/0x468
[  258.490776]  worker_thread+0x40/0x450
[  258.494424]  kthread+0x128/0x130
[  258.497639]  ret_from_fork+0x10/0x1c
[  258.501329] INFO: task flr.sh:4534 blocked for more than 120 seconds.
[  258.507742]       Tainted: G         C O      5.1.0-rc1-ge2e3ca0 #1
[  258.513980] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  258.521774] flr.sh          D    0  4534   4504 0x00000000
[  258.527235] Call trace:
[  258.529671]  __switch_to+0xb4/0x1b8
[  258.533146]  __schedule+0x1ec/0x720
[  258.536619]  schedule+0x38/0x90
[  258.539749]  rwsem_down_write_failed+0x14c/0x210
[  258.544347]  down_write+0x48/0x60
[  258.547648]  pci_device_add+0x1a0/0x290
[  258.551469]  pci_iov_add_virtfn+0x190/0x358
[  258.555633]  sriov_enable+0x24c/0x480
[  258.559279]  pci_enable_sriov+0x14/0x28
[  258.563101]  hisi_zip_sriov_configure+0x64/0x100 [hisi_zip]
[  258.568649]  sriov_numvfs_store+0xc4/0x190
[  258.572728]  dev_attr_store+0x18/0x28
[  258.576375]  sysfs_kf_write+0x3c/0x50
[  258.580024]  kernfs_fop_write+0x114/0x1d8
[  258.584018]  __vfs_write+0x18/0x38
[  258.587404]  vfs_write+0xa4/0x1b0
[  258.590705]  ksys_write+0x60/0xd8
[  258.594007]  __arm64_sys_write+0x18/0x20
[  258.597914]  el0_svc_common+0x5c/0x100
[  258.601646]  el0_svc_handler+0x2c/0x80
[  258.605381]  el0_svc+0x8/0xc
[  379.243461] INFO: task kworker/0:1:13 blocked for more than 241 seconds.
[  379.250134]       Tainted: G         C O      5.1.0-rc1-ge2e3ca0 #1
[  379.256373] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.


Thank you,
Jay



https://www.spinics.net/lists/linux-pci/msg83508.html