Hi, Are there any further advice? On 2019/6/5 7:47, Benjamin Herrenschmidt wrote: > On Tue, 2019-06-04 at 10:34 -0400, Sinan Kaya wrote: >> On 6/3/19, Fangjian (Turing) <f.fangjian@xxxxxxxxxx> wrote: >>> 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 >> >> Should we replace these device lock with try lock loop with some sleep >> statements. This could solve the immediate deadlock issues until >> someone implements granular locking in pci. > > That won't necessarily solve this AB->BA problem. I think the issue > here is that sriov shouldn't device_lock before doing something that > can take the pci_bus_sem. > > Ben. > > >>> 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 >>> >>> > > > . >
