avahi-daemon spinning, using 65% of a CPU after connection to Les Schwab wifi

[Steve Langasek]

After connecting to a guest wifi, I notice that avahi-daemon is using an unreasonable amount of CPU time on my laptop.

gdb shows a busy loop in avahi_simple_poll_iterate().

strace output looks like:

write(7, "W", 1) = 1
write(7, "W", 1) = 1
read(6, "WW", 10) = 2
poll([{fd=6, events=POLLIN}, {fd=16, events=POLLIN}, {fd=15, events=POLLIN}, {fd=14, events=POLLIN}, {fd=13, events=POLLIN}, {fd=12, events=POLLIN}, {fd=11, events=POLLIN}, {fd=10, events=POLLIN}, {fd=3, events=POLLIN}, {fd=8, events=POLLIN}], 10, 0) = 4 ([{fd=16, revents=POLLIN}, {fd=13, revents=POLLIN}, {fd=12, revents=POLLIN}, {fd=10, revents=POLLIN}])
write(7, "W", 1) = 1
write(7, "W", 1) = 1
read(6, "WW", 10) = 2
poll([{fd=6, events=POLLIN}, {fd=16, events=POLLIN}, {fd=15, events=POLLIN}, {fd=14, events=POLLIN}, {fd=13, events=POLLIN}, {fd=12, events=POLLIN}, {fd=11, events=POLLIN}, {fd=10, events=POLLIN}, {fd=3, events=POLLIN}, {fd=8, events=POLLIN}], 10, 0) = 4 ([{fd=16, revents=POLLIN}, {fd=13, revents=POLLIN}, {fd=12, revents=POLLIN}, {fd=10, revents=POLLIN}])
write(7, "W", 1) = 1
write(7, "W", 1) = 1
write(7, "W", 1) = 1
write(7, "W", 1) = 1
read(6, "WWWW", 10) = 4
poll([{fd=6, events=POLLIN}, {fd=16, events=POLLIN}, {fd=15, events=POLLIN}, {fd=14, events=POLLIN}, {fd=13, events=POLLIN}, {fd=12, events=POLLIN}, {fd=11, events=POLLIN}, {fd=10, events=POLLIN}, {fd=3, events=POLLIN}, {fd=8, events=POLLIN}], 10, 0) = 4 ([{fd=16, revents=POLLIN}, {fd=13, revents=POLLIN}, {fd=12, revents=POLLIN}, {fd=10, revents=POLLIN}])
write(7, "W", 1) = 1
write(7, "W", 1) = 1
write(7, "W", 1) = 1
write(7, "W", 1) = 1
read(6, "WWWW", 10) = 4
poll([{fd=6, events=POLLIN}, {fd=16, events=POLLIN}, {fd=15, events=POLLIN}, {fd=14, events=POLLIN}, {fd=13, events=POLLIN}, {fd=12, events=POLLIN}, {fd=11, events=POLLIN}, {fd=10, events=POLLIN}, {fd=3, events=POLLIN}, {fd=8, events=POLLIN}], 10, 0) = 4 ([{fd=16, revents=POLLIN}, {fd=13, revents=POLLIN}, {fd=12, revents=POLLIN}, {fd=10, revents=POLLIN}])
[...]

(repeats endlessly)

fd 6 and 7 are two ends of a pipe that avahi-daemon has open to itself.

It looks like avahi-daemon /eventually/ settles down, but this takes a long time.

I'm not sure what to look for to explain this busy looping.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: avahi-daemon 0.7-4ubuntu2.1
ProcVersionSignature: Ubuntu 4.18.0-14.15-generic 4.18.20
Uname: Linux 4.18.0-14-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.10-0ubuntu13.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Mar 9 11:27:05 2019
InstallationDate: Installed on 2010-09-24 (3088 days ago)
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
SourcePackage: avahi
UpgradeStatus: Upgraded to cosmic on 2018-10-18 (141 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.