That didn't fix it. So, next I uninstalled nscd. At this point, nothing else in apt's purview explicitly depended on it - though it was still showing up in straces.
After that, the behavior has been significantly better so far. So... maybe a bug in nscd? On that note, just curious: why is nscd showing up in an strace when the root user - having logged in at the console at ctrl-alt-F2, with no GUI - is trying to open a file using vim in its home directory? -- 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/1886022 Title: multiple processes intermittently stall at same point in strace Status in linux package in Ubuntu: Incomplete Bug description: If this isn't a kernel bug, my apologies. I didn't know where else to put it. It affects seemingly unrelated processes, so there wasn't an obvious 'package'. Possibly nscd, which is in glibc, which is close to the kernel... I noticed frequent, but intermittent hangs/stalls in multiple processes. The processes usually go on to completion after a few seconds or so. Occasionally, I get timeouts that I think might be this same symptom but aren't always strace-able. At first, I thought it was an authentication issue because I got hangs with "sudo -i" as well as intermittently very slow logins via ssh with ldap. But, then it happened with "vim dum", which could still be authentication somehow, but I don't know enough to determine that. Htop will also hang intermittently, but I don't have a trace of it. I started running strace on the processes that are hanging. The hang happened after the same few lines each time that I was able to strace at the same time of a hang (it is intermittent). Here is an example of the last lines before hang where a normal user issues "strace id username": socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3 connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = 0 sendto(3, "\2\0\0\0\v\0\0\0\7\0\0\0passwd\0", 19, MSG_NOSIGNAL, NULL, 0) = 19 poll([{fd=3, events=POLLIN|POLLERR|POLLHUP}], 1, 5000^Cstrace: Process 2816 detached <detached ...> I hit ctrl-C to stop execution so I could easily copy that info, hence detached. Here is an example from root using "strace vim dum": socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0) = 3 connect(3, {sa_family=AF_UNIX, sun_path="/var/run/nscd/socket"}, 110) = 0 sendto(3, "\2\0\0\0\v\0\0\0\7\0\0\0passwd\0", 19, MSG_NOSIGNAL, NULL, 0) = 19 poll([{fd=3, events=POLLIN|POLLERR|POLLHUP}], 1, 5000 ...that took practice to capture. I suspect that LDAP is involved somehow, but it might be victim rather than culprit. Obviously, nscd has some involvement per the lines above. Or possibly, these lines are about strace itself? I can capture full straces with timings, etc. Just say what you need. Or direct me to the proper venue for this report. I looked in kern.log for evidence of a hardware issue, but didn't see anything that looked significantly unusual. If it seems like hardware, I will appreciate hints as to the component. ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: linux-image-5.4.0-40-generic 5.4.0-40.44 ProcVersionSignature: Ubuntu 5.4.0-40.44-generic 5.4.44 Uname: Linux 5.4.0-40-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.20.11-0ubuntu27.3 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: installer 1846 F.... pulseaudio CasperMD5CheckResult: skip CurrentDesktop: LXDE Date: Thu Jul 2 04:36:12 2020 InstallationDate: Installed on 2020-06-25 (7 days ago) InstallationMedia: Ubuntu-MATE 20.04 LTS "Focal Fossa" - Release amd64 (20200423) MachineType: HP ProLiant DL380 G7 ProcFB: 0 VESA VGA ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-40-generic root=UUID=be36c28f-47f3-4536-8bb3-8b2f3856fa42 ro quiet splash vt.handoff=7 RelatedPackageVersions: linux-restricted-modules-5.4.0-40-generic N/A linux-backports-modules-5.4.0-40-generic N/A linux-firmware 1.187.1 RfKill: SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 05/05/2011 dmi.bios.vendor: HP dmi.bios.version: P67 dmi.chassis.type: 23 dmi.chassis.vendor: HP dmi.modalias: dmi:bvnHP:bvrP67:bd05/05/2011:svnHP:pnProLiantDL380G7:pvr:cvnHP:ct23:cvr: dmi.product.family: ProLiant dmi.product.name: ProLiant DL380 G7 dmi.product.sku: 583917-B21 dmi.sys.vendor: HP To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1886022/+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
