Hello,
On Linux 6.0.0-rc3, disconnecting a mounted pendrive with opened files causes these symptoms:
- "task kworker/X blocked for more than Y seconds" warnings (see below) are repeatedly printed in dmesg,
- after reconnecting the pendrive (or possibly other USB devices), it is not detected,
- the login screen (Gnome on Ubuntu 20.04) freezes for some time (around 20s), due to a hang in colord-sane.
These symptoms disappear after closing the opened files (and perhaps also directories) on the pendrive.
I am aware that disconnecting a pendrive with a mounted filesystem is unwise, but many people do so
nonetheless.
I have bisected this down to
commit 16728aaba62e ("scsi: core: Make sure that hosts outlive targets")
With the previous
commit fe442604199e ("scsi: core: Make sure that targets outlive devices")
the problem does not happen.
To reproduce:
1. Plug a pendrive into a USB port (checked with a pendrive formatted with a FAT32 filesystem).
2. Mount it, open a file on this pendrive with the "less" command-line program.
3. Optionally suspend the system to RAM.
4. Disconnect the pendrive.
5. Resume the system, if it was suspended.
Warnings from dmesg:
[ 76.212690] usb 1-3.4.3: USB disconnect, device number 6
[ 76.219765] device offline error, dev sdc, sector 2049 op 0x1:(WRITE) flags 0x100000 phys_seg 1 prio class 2
[ 76.219791] Buffer I/O error on dev sdc1, logical block 1, lost async page write
[ 242.764446] INFO: task kworker/0:7:1701 blocked for more than 120 seconds.
[ 242.764463] Tainted: G E 6.0.0-rc3mj6 #239
[ 242.764470] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 242.764474] task:kworker/0:7 state:D stack: 0 pid: 1701 ppid: 2 flags:0x00004000
[ 242.764488] Workqueue: usb_hub_wq hub_event
[ 242.764504] Call Trace:
[ 242.764507] <TASK>
[ 242.764514] __schedule+0x2c5/0xcd0
[ 242.764527] schedule+0x5d/0xf0
[ 242.764535] scsi_remove_host+0x163/0x1b0
[ 242.764547] ? var_wake_function+0x60/0x60
[ 242.764559] usb_stor_disconnect+0x50/0xd0 [usb_storage]
[ 242.764571] usb_unbind_interface+0x8c/0x240
[ 242.764581] device_remove+0x64/0x70
[ 242.764590] device_release_driver_internal+0xd1/0x160
[ 242.764599] device_release_driver+0x12/0x20
[ 242.764608] bus_remove_device+0xde/0x150
[ 242.764616] device_del+0x192/0x3e0
[ 242.764621] ? usb_remove_ep_devs+0x1f/0x30
[ 242.764632] usb_disable_device+0xab/0x240
[ 242.764639] usb_disconnect+0xc7/0x260
[ 242.764647] ? set_port_feature+0x37/0x40
[ 242.764656] hub_event+0xeb0/0x17c0
[ 242.764668] ? __schedule+0x2cd/0xcd0
[ 242.764675] ? queue_rcu_work+0x2c/0x40
[ 242.764684] process_one_work+0x21c/0x3c0
[ 242.764693] worker_thread+0x4a/0x3b0
[ 242.764703] ? process_one_work+0x3c0/0x3c0
[ 242.764711] kthread+0xcf/0xf0
[ 242.764719] ? kthread_complete_and_exit+0x20/0x20
[ 242.764728] ret_from_fork+0x22/0x30
[ 242.764737] </TASK>
The kernel is tainted AFAIK because of the following:
[ 0.442486] backlight: module verification failed: signature and/or required key missing - tainting kernel
[...]
[ 0.446462] Loading compiled-in X.509 certificates
[ 0.447431] Loaded X.509 cert 'Build time autogenerated kernel key: cbf6b5d58385db4124f3ddd5fa0457b112415dcb'
The module was loaded before the signing keys were processed - which is an unrelated bug, present since a long time.
System information:
- Ubuntu 20.04 amd64,
- HP 17-by0001nw laptop,
- problem happens also when using an external USB 3.0 UNITEK hub.
Greetings,
Mateusz Jończyk
