Public bug reported:
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
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Confirmed
** Tags: amd64 apport-bug focal
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https://bugs.launchpad.net/bugs/1886022
Title:
multiple processes intermittently stall at same point in strace
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