This bug was fixed in the package cups-browsed - 2.0~rc1-0ubuntu1.1
---------------
cups-browsed (2.0~rc1-0ubuntu1.1) lunar; urgency=medium
* Fixed handling of failures when creating local print queues. On
a failure a global variable was set by the queue creation function
running as background thread, to stop the loop for updating the
local queues, but the variable was never reset, making no local
queue updates done any more for the rest of the life of the
daemon, making the daemon falling into a busy loop. Completely
done away with the variable. It is actually not needed (LP: #2018504).
-- Till Kamppeter <till.kamppe...@gmail.com> Sun, 4 Jun 2023 18:50:57
+0200
** Changed in: cups-browsed (Ubuntu Lunar)
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/2018504
Title:
cups-browsed is using an excessive amount of CPU
Status in cups-browsed package in Ubuntu:
Fix Released
Status in cups-browsed source package in Lunar:
Fix Released
Bug description:
[ Impact ]
One observes that a certain time after booting cups-browsed suddenly
starts to occupy a certain percentage or all of one CPU core. This
slows down other processes on the system, consumes battery power,
causes noise of the CPU fan.
It does not require to have any local printers set up on ones machine,
but there must be printers available in the local network.
A typical trigger for this bug is a sudden disappearing of a printer
in the network, for example if a laptop shares a printer and it gets
suspended by closing the lid. This way the shared printer most
probably disappears without the laptop's Avahi sending out some
"disappered" notification.
cups-browsed does not recover from the failure, once failed it
consumes CPU and stops working, until being restarted, for most with
the next boot.
The problem got introduced on the transition from cups-browsed 1.x to
2.x (in Ubuntu 23.04). cups-browsed got a multi-threading feature
added to be able to create more local queues at a time, especially
when there are many printers available in the network..
The bug is in the error handling: If cups-browsed fails to access a
remote printer in a sub-thread, it sets a flag to inform the main
thread, to stop an update loop. The main thread misses to reset the
flag once it has stopped the loop and so any further update loop
during the rest of the life of cups-browsed gets stopped immediately,
no printers updated at all, and as because of the updates not
performed, updates are still needed and so the loop called again
immediately, ending up in an infinite busy loop.
And these access errors happen especially if a remote printer goes
away without any DNS-SD/Avahi notification about it disappearing.
So not only CPU load is caused but cups-browsed ceases completely to
work.
[ Test Plan ]
This bug is not easy to reproduce, but at least for everyone who
reported it here it occurs again and again. So everyone already
suffering it is asked to test the proposed SRU package.
To try to reproduce it one ideally takes 2 computers, one running
Ubuntu 23.04 with the affected cups-browsed (the client) and one
running any Linux and sharing printers by means of CUPS queues,
Printer Applications, or the ippeveprinter utility (the server).
Some ways to try to trigger the failure on the client:
- Suspend the server, either by closing its laptpp lid or by selecting the
"Suspend" function in its desktop's menus.
- On the server start a Printer Application or ippeveprinter manually (this
way
no systemd watch dog applies to it). Then hard-kill its process with "kill
-9
...".
- If the server is connected to the local network only by wired Ethernet,
unplug
its Ethernet cable.
- If the server is connected to the local network only by Wi-Fi, switch it
into
flight mode.
All these methods should make (a) shared printer(s) on the server go
away without getting it properly de-registered from Avahi on the
server, and so no notification being broadcasted into the local
network. So the client's cups-browsed would not remove the
corresponding local print queue and keep maintaining it, sooner or
later failing to access the printer and then getting stuck as
described above.
Anyone who is suffering this bug could also simply install the
proposed package and observe and when the CPU load by cups-browsed
does not appear again after some days consider the fix as verified.
[ Where problems could occur ]
The fix does nothing more than removing the mentioned flag, and
instead mark the remote printer as disappeared. This way the update
loop is not stopped but finishes normally, which is no problem as the
remote printers are independent, there is no reason to skip updating
printers because one printer failed.
After the update loop having completed, in the next update loop the
local queue for the faulty printer gets removed, as it is marked as
disappeared.
If cups-browsed gets notified about a disappeared printer by Avahi, it
also marks it as disappeared so that the queue gets removed in the
next update loop. So now we do the same with faulty printers, which
simply do not answer to an IPP request.
As the regular procedure when a remote printer gets shut down works
correctly we do not actually expect regressions here.
[ Original Description ]
It could be a problem with the network, but I'm seeing cups-browsed
appearing to keep one CPU core busy. According to systemctl, it has
used 51 minutes of CPU time since being started 6 hours ago (the
laptop has been suspended a few times in that time):
Active: active (running) since Thu 2023-05-04 08:41:36 CEST; 6h ago
Main PID: 68281 (cups-browsed)
Tasks: 4 (limit: 18785)
Memory: 7.0M
CPU: 51min 32.735s
This seems surprising, since I'd only expect it to be doing something
when printers are advertised over mDNS.
It may be unrelated, but I'm also seeing warnings like the following
in the journal:
May 04 14:26:11 lrrr cups-browsed[68281]: Source ID 1207266864 was not
found when attempting to remove it
May 04 14:26:11 lrrr cups-browsed[68281]: Source ID 1207318247 was not
found when attempting to remove it
May 04 14:26:11 lrrr cups-browsed[68281]: Source ID 1207362184 was not
found when attempting to remove it
May 04 14:26:11 lrrr cups-browsed[68281]: Source ID 1207375185 was not
found when attempting to remove it
May 04 14:38:28 lrrr cups-browsed[68281]: Source ID 1303173242 was not
found when attempting to remove it
May 04 14:38:28 lrrr cups-browsed[68281]: Source ID 1303188526 was not
found when attempting to remove it
May 04 14:38:28 lrrr cups-browsed[68281]: Source ID 1303229832 was not
found when attempting to remove it
May 04 14:38:28 lrrr cups-browsed[68281]: Source ID 1303249965 was not
found when attempting to remove it
May 04 14:38:28 lrrr cups-browsed[68281]: Source ID 1303265399 was not
found when attempting to remove it
May 04 14:38:39 lrrr cups-browsed[68281]: Source ID 1304615115 was not
found when attempting to remove it
May 04 14:50:48 lrrr cups-browsed[68281]: Source ID 1398290009 was not
found when attempting to remove it
May 04 14:50:48 lrrr cups-browsed[68281]: Source ID 1398304338 was not
found when attempting to remove it
May 04 14:50:48 lrrr cups-browsed[68281]: Source ID 1398387203 was not
found when attempting to remove it
May 04 14:50:51 lrrr cups-browsed[68281]: Source ID 1398664816 was not
found when attempting to remove it
May 04 14:50:51 lrrr cups-browsed[68281]: Source ID 1398674240 was not
found when attempting to remove it
May 04 14:50:51 lrrr cups-browsed[68281]: Source ID 1398687187 was not
found when attempting to remove it
May 04 14:50:51 lrrr cups-browsed[68281]: Source ID 1398698982 was not
found when attempting to remove it
May 04 14:50:51 lrrr cups-browsed[68281]: Source ID 1398726803 was not
found when attempting to remove it
May 04 14:52:24 lrrr cups-browsed[68281]: Source ID 1410715532 was not
found when attempting to remove it
May 04 14:52:24 lrrr cups-browsed[68281]: Source ID 1410741036 was not
found when attempting to remove it
May 04 14:52:24 lrrr cups-browsed[68281]: Source ID 1410777106 was not
found when attempting to remove it
May 04 14:52:25 lrrr cups-browsed[68281]: Source ID 1410797157 was not
found when attempting to remove it
These errors seem to be generated when glib's g_source_remove()
function is called with an ID for a job that doesn't exist. This could
indicate that cups-browsed is losing track of an idle or timeout
function.
ProblemType: Bug
DistroRelease: Ubuntu 23.04
Package: cups-browsed 2.0~rc1-0ubuntu1
ProcVersionSignature: Ubuntu 6.2.0-20.20-generic 6.2.6
Uname: Linux 6.2.0-20-generic x86_64
ApportVersion: 2.26.1-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Thu May 4 15:10:03 2023
InstallationDate: Installed on 2017-09-02 (2070 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170901)
MachineType: LENOVO 20HRCTO1WW
Papersize: a4
PpdFiles:
Error: command ['fgrep', '-H', '*NickName',
'/etc/cups/ppd/Lexmark_MS610dn_3_.ppd', '/etc/cups/ppd/test6_59CD60.ppd',
'/etc/cups/ppd/HP_OfficeJet_Pro_8710_C7327F.ppd',
'/etc/cups/ppd/test4_F7866E.ppd',
'/etc/cups/ppd/HP_Smart_Tank_530_series_E23C83.ppd'] failed with exit code 2:
grep: /etc/cups/ppd/Lexmark_MS610dn_3_.ppd: Permission denied
grep: /etc/cups/ppd/test6_59CD60.ppd: Permission denied
grep: /etc/cups/ppd/HP_OfficeJet_Pro_8710_C7327F.ppd: Permission denied
grep: /etc/cups/ppd/test4_F7866E.ppd: Permission denied
grep: /etc/cups/ppd/HP_Smart_Tank_530_series_E23C83.ppd: Permission denied
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.2.0-20-generic
root=UUID=94446fd9-8625-46ee-a8de-034cc22d680b ro quiet splash vt.handoff=7
SourcePackage: cups-browsed
UpgradeStatus: Upgraded to lunar on 2023-03-29 (36 days ago)
dmi.bios.date: 11/24/2022
dmi.bios.release: 1.57
dmi.bios.vendor: LENOVO
dmi.bios.version: N1MET72W (1.57 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20HRCTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.22
dmi.modalias:
dmi:bvnLENOVO:bvrN1MET72W(1.57):bd11/24/2022:br1.57:efr1.22:svnLENOVO:pn20HRCTO1WW:pvrThinkPadX1Carbon5th:rvnLENOVO:rn20HRCTO1WW:rvrNotDefined:cvnLENOVO:ct10:cvrNone:skuLENOVO_MT_20HR_BU_Think_FM_ThinkPadX1Carbon5th:
dmi.product.family: ThinkPad X1 Carbon 5th
dmi.product.name: 20HRCTO1WW
dmi.product.sku: LENOVO_MT_20HR_BU_Think_FM_ThinkPad X1 Carbon 5th
dmi.product.version: ThinkPad X1 Carbon 5th
dmi.sys.vendor: LENOVO
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