Hi
We do some test to trigger hotplug while do sysfs "remove" operation,
then met a deadlock issue.
pciehp 0000:00:0c.0:pcie004: Slot(0-1): Link Up
echo 1 > 0000\:00\:0c.0/remove
PME and hotplug share an MSI/MSI-X vector.
The sysfs "remove" operation will call the below function.
remove_store()
pci_stop_and_remove_bus_device_locked()
pci_lock_rescan_remove()
pci_stop_and_remove_bus_device()
...
pcie_pme_remove()
synchronize_irq() // Here will wait for hotplug IRQ handler
pci_unlock_rescan_remove();
Hotplug
pciehp_ist()
pciehp_handle_presence_or_link_change()
pciehp_configure_device()
pci_lock_rescan_remove() // Here will wait the pci_unlock_rescan_remove()
So met the deadlock issue. Any idea to solve such issue ?
2180.490703] INFO: task bash:10913 blocked for more than 120 seconds.
[ 2180.503428] Tainted: P OE 4.19.5-1.1.29.aarch64 #1
[ 2180.516496] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 2180.532176] bash D 0 10913 6565 0x00000200
# ps -ax |grep D
PID TTY STAT TIME COMMAND
10913 ttyAMA0 Ds+ 0:00 -bash
12945 ? Ss 0:00 /usr/sbin/sshd -D
14022 ? D 0:00 [irq/745-pciehp]
15972 pts/1 S+ 0:00 grep --color=auto D
# cat /proc/14022/stack
[<0>] __switch_to+0x94/0xd8
[<0>] pci_lock_rescan_remove+0x20/0x28
[<0>] pciehp_configure_device+0x30/0x140
[<0>] pciehp_handle_presence_or_link_change+0x324/0x458
[<0>] pciehp_ist+0x1dc/0x1e0
[<0>] irq_thread_fn+0x30/0x90
[<0>] irq_thread+0x140/0x210
[<0>] kthread+0x134/0x138
[<0>] ret_from_fork+0x10/0x1c
[<0>] 0xffffffffffffffff
# cat /proc/10913/stack
[<0>] __switch_to+0x94/0xd8
[<0>] synchronize_irq+0x8c/0xc0
[<0>] pcie_pme_suspend+0xa4/0x118
[<0>] pcie_pme_remove+0x20/0x40
[<0>] pcie_port_remove_service+0x3c/0x58
[<0>] device_release_driver_internal+0x1b4/0x250
[<0>] device_release_driver+0x28/0x38
[<0>] bus_remove_device+0xd4/0x160
[<0>] device_del+0x128/0x348
[<0>] device_unregister+0x24/0x78
[<0>] remove_iter+0x48/0x58
[<0>] device_for_each_child+0x6c/0xb8
[<0>] pcie_port_device_remove+0x2c/0x48
[<0>] pcie_portdrv_remove+0x68/0x78
[<0>] pci_device_remove+0x48/0x120
[<0>] device_release_driver_internal+0x1b4/0x250
[<0>] device_release_driver+0x28/0x38
[<0>] pci_stop_bus_device+0x84/0xc0
[<0>] pci_stop_and_remove_bus_device_locked+0x24/0x40
[<0>] remove_store+0xa4/0xb8
[<0>] dev_attr_store+0x44/0x60
[<0>] sysfs_kf_write+0x58/0x80
[<0>] kernfs_fop_write+0xd8/0x1e0
[<0>] __vfs_write+0x60/0x190
[<0>] vfs_write+0xac/0x1c0
[<0>] ksys_write+0x6c/0xd8
[<0>] __arm64_sys_write+0x24/0x30
[<0>] el0_svc_common+0x78/0x100
[<0>] el0_svc_handler+0x38/0x88
[<0>] el0_svc+0x8/0xc
[<0>] 0xffffffffffffffff
Thanks,
Dongdong
