on Obuntu 20 LTS the same bug also exists, but with slightly different symptoms, see bug https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1905994 #1905994
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1905782 Title: kernel freeze on USB disconnect after failure to set rts/dts on USB VCP device Status in linux package in Ubuntu: Confirmed Bug description: When plugging in a USB device on Ubuntu 18.04 that offers a virtual modem/com port (typically /dev/ttyACM0) then the "modemmanager" service will try to configure this modem/serial port automatically without user interaction, setting dtr/rts parameters. However sometimes USB modem devices are used as a generic serial interface to hardware internals, without an actual serial line connected. Setting dtr/rts makes no sense in this context, and this feature might be unsupported. This, however, triggers a faulty code path in the linux kernel that on device disconnect causes a kworker process to freeze - blocking the CPU core it is running on indefinitely. This in turn has catastrophic effects on system stability. Some IO calls, that run on other cores, will work without problem, while those scheduled on the same core will never execute. Although no "OOPS" or "PANIC" is generated, the situation is dire, as the system typically can not be shutdown or rebooted, and during tests I ended up with file system corruption in a few cases that could not be fixed by a simple journal recovery To trigger this bug, several side-conditions need to be met: 1. A USB device needs to be plugged in that provides a virtual com port 2. The device must not support setting of DTR/RTS parameters 3. A program must try to set these via ioctls 4. The device must then be disconnected --> Kernel freeze On Ubuntu "3." is always guaranteed, if modemmanager is installed and the service is running Please contact me if you need additional information about how to reproduce this. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: linux-image-4.15.0-124-generic 4.15.0-124.127 ProcVersionSignature: Ubuntu 4.15.0-124.127-generic 4.15.18 Uname: Linux 4.15.0-124-generic x86_64 ApportVersion: 2.20.9-0ubuntu7.20 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: raven 2039 F.... pulseaudio CurrentDesktop: XFCE Date: Thu Nov 26 20:30:58 2020 EcryptfsInUse: Yes HibernationDevice: #RESUME=UUID=de4646dc-eb1a-4530-b6bc-df659b641728 RESUME=none InstallationDate: Installed on 2017-04-28 (1308 days ago) InstallationMedia: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2) MachineType: FUJITSU LIFEBOOK E736 ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-124-generic root=/dev/mapper/ubuntu--vg-root ro "acpi_osi=!Windows 2012" RelatedPackageVersions: linux-restricted-modules-4.15.0-124-generic N/A linux-backports-modules-4.15.0-124-generic N/A linux-firmware 1.173.19 SourcePackage: linux UpgradeStatus: Upgraded to bionic on 2019-06-28 (517 days ago) dmi.bios.date: 12/20/2016 dmi.bios.vendor: FUJITSU // Insyde Software Corp. dmi.bios.version: Version 1.22 dmi.board.name: FJNB293 dmi.board.vendor: FUJITSU dmi.board.version: M4 dmi.chassis.type: 10 dmi.chassis.vendor: FUJITSU dmi.chassis.version: LIFEBOOK E736 dmi.modalias: dmi:bvnFUJITSU//InsydeSoftwareCorp.:bvrVersion1.22:bd12/20/2016:svnFUJITSU:pnLIFEBOOKE736:pvr10601115935:rvnFUJITSU:rnFJNB293:rvrM4:cvnFUJITSU:ct10:cvrLIFEBOOKE736: dmi.product.family: LIFEBOOK-FTS dmi.product.name: LIFEBOOK E736 dmi.product.version: 10601115935 dmi.sys.vendor: FUJITSU To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1905782/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
