When the Attention button on a PCIE slot is pressed, 5 seconds later, pciehp_power_thread() will be scheduled on slot->wq. This function will get a global mutex lock 'pci_rescan_remove_lock' in pciehp_unconfigure_device().
At the same time, we remove the pcie port by sysfs, which results in pci_stop_and_remove_bus_device_locked() called. This function will get the global mutex lock 'pci_rescan_remove_lock', and then release the struct 'ctrl', which will wait until the work_struct on slot->wq is finished.
If pci_stop_and_remove_bus_device_locked() got the mutex lock, and before it drains workqueue slot->wq, pciehp_power_thread() is scheduled on slot->wq and tries to get the mutex lock. Then pci_stop_and_remove_bus_device_locked() tries to drain workqueue slot->wq and wait until work struct 'pciehp_power_thread()' is finished. Then a hung_task happens.
This patch solve this problem by schedule 'pciehp_power_thread()' on a system workqueue instead of slot->wq.
The Call Trace we got is as following.
INFO: task kworker/0:2:4413 blocked for more than 120 seconds. Tainted: P W O 4.12.0-rc1 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:2 D 0 4413 2 0x00000000 Workqueue: pciehp-0 pciehp_power_thread Call trace: [<ffff0000080861d4>] __switch_to+0x94/0xa8 [<ffff000008bea9c0>] __schedule+0x1b0/0x708 [<ffff000008beaf58>] schedule+0x40/0xa4 [<ffff000008beb33c>] schedule_preempt_disabled+0x28/0x40 [<ffff000008bec1dc>] __mutex_lock.isra.8+0x148/0x50c [<ffff000008bec5c4>] __mutex_lock_slowpath+0x24/0x30 [<ffff000008bec618>] mutex_lock+0x48/0x54 [<ffff0000084d8188>] pci_lock_rescan_remove+0x20/0x28 [<ffff0000084f87c0>] pciehp_unconfigure_device+0x54/0x1cc [<ffff0000084f8260>] pciehp_disable_slot+0x4c/0xbc [<ffff0000084f8370>] pciehp_power_thread+0xa0/0xb8 [<ffff0000080e9ce8>] process_one_work+0x13c/0x3f8 [<ffff0000080ea004>] worker_thread+0x60/0x3e4 [<ffff0000080f0814>] kthread+0x10c/0x138 [<ffff0000080836c0>] ret_from_fork+0x10/0x50 INFO: task bash:31732 blocked for more than 120 seconds. Tainted: P W O 4.12.0-rc1 #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. bash D 0 31732 1 0x00000009 Call trace: [<ffff0000080861d4>] __switch_to+0x94/0xa8 [<ffff000008bea9c0>] __schedule+0x1b0/0x708 [<ffff000008beaf58>] schedule+0x40/0xa4 [<ffff000008bee7b4>] schedule_timeout+0x1a0/0x340 [<ffff000008bebb88>] wait_for_common+0x108/0x1bc [<ffff000008bebc64>] wait_for_completion+0x28/0x34 [<ffff0000080e7594>] flush_workqueue+0x130/0x488 [<ffff0000080e79b0>] drain_workqueue+0xc4/0x164 [<ffff0000080ec3cc>] destroy_workqueue+0x28/0x1f4 [<ffff0000084fa094>] pciehp_release_ctrl+0x34/0xe0 [<ffff0000084f75b0>] pciehp_remove+0x30/0x3c [<ffff0000084f24d8>] pcie_port_remove_service+0x3c/0x54 [<ffff00000876b1e4>] device_release_driver_internal+0x150/0x1d0 [<ffff00000876b28c>] device_release_driver+0x28/0x34 [<ffff00000876a018>] bus_remove_device+0xe0/0x11c [<ffff000008766348>] device_del+0x200/0x304 [<ffff00000876646c>] device_unregister+0x20/0x38 [<ffff0000084f2560>] remove_iter+0x44/0x54 [<ffff000008765230>] device_for_each_child+0x4c/0x90 [<ffff0000084f2c98>] pcie_port_device_remove+0x2c/0x48 [<ffff0000084f2f48>] pcie_portdrv_remove+0x60/0x6c [<ffff0000084e3de4>] pci_device_remove+0x48/0x110 [<ffff00000876b1e4>] device_release_driver_internal+0x150/0x1d0 [<ffff00000876b28c>] device_release_driver+0x28/0x34 [<ffff0000084db028>] pci_stop_bus_device+0x9c/0xac [<ffff0000084db190>] pci_stop_and_remove_bus_device_locked+0x24/0x3c [<ffff0000084e5eb0>] remove_store+0x74/0x80 [<ffff000008764680>] dev_attr_store+0x44/0x5c [<ffff0000082e7e1c>] sysfs_kf_write+0x5c/0x74 [<ffff0000082e7014>] kernfs_fop_write+0xcc/0x1dc [<ffff0000082602e0>] __vfs_write+0x48/0x13c [<ffff00000826174c>] vfs_write+0xa8/0x198 [<ffff000008262ce8>] SyS_write+0x54/0xb0 [<ffff000008083730>] el0_svc_naked+0x24/0x28
Signed-off-by: Xiongfeng Wang wangxiongfeng2@huawei.com --- drivers/pci/hotplug/pciehp_ctrl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c index 83f3d4a..9d39d85 100644 --- a/drivers/pci/hotplug/pciehp_ctrl.c +++ b/drivers/pci/hotplug/pciehp_ctrl.c @@ -221,7 +221,7 @@ static void pciehp_queue_power_work(struct slot *p_slot, int req) info->p_slot = p_slot; INIT_WORK(&info->work, pciehp_power_thread); info->req = req; - queue_work(p_slot->wq, &info->work); + schedule_work(&info->work); }
void pciehp_queue_pushbutton_work(struct work_struct *work)