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https://issues.apache.org/jira/browse/GUACAMOLE-2118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18100758#comment-18100758
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Jason Keltz commented on GUACAMOLE-2118:
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[~mjumper] I believe because of the change in thread naming in 1.6.1, it's 1
guacd process with many named threads ... (pull 674).
% pstree -p 1132502 -T
guacd(1132502)─┬─rdp an****r2@cr(1292149)
├─rdp br****et@he(1260889)
├─rdp br****et@he(1291155)
├─rdp en****om@he(1243537)
├─rdp er****06@ro(1293058)
├─rdp et****en@cr(1192976)
├─rdp ha****ur@lc(1170880)
├─rdp mi****7s@ne(1170621)
├─rdp pr****i4@re(1293368)
├─rdp ra****an@ne(1296338)
├─rdp rd****ce@br(1295793)
├─rdp rd****ce@re(1284305)
├─rdp rp****di@re(1284427)
└─rdp sh****21@cr(1297764)
So now we have 14 active guacd but 9 active logins so we've grown one stuck
thread in the day... (when the fall term starts, there will be many more users
logging in at once, and this is likely to grow quicker.)..
[~vnick] has access to the system in question, and if available could run
testing that you suggest. If you let me know what to run, I will do my best to
run. I'm happy to provide you with access as well as required.
Also, I noticed this segfault in dmesg and I didn't realize it was related to
guacd as well:
----
[Wed Jul 29 13:35:36 2026] user-input[1159204]: segfault at 7f7028000160 ip
00007f7028000160 sp 00007f6f72ffcc48 error 15
[Wed Jul 29 13:35:36 2026] Code: 00 00 50 e9 09 28 70 7f 00 00 30 01 00 28 70
7f 00 00 30 01 00 28 70 7f 00 00 50 a1 06 28 70 7f 00 00 50 a1 06 28 70 7f 00
00 <10> bf 3d 28 70 7f 00 00 10 bf 3d 28 70 7f 00 00 60 01 00 28 70 7f
----
According to my AI friend:
----
What error 15 Means in Practice
Because the Instruction Pointer (ip) and the faulting address are identical,
and error 15 signifies an instruction fetch fault on non-executable memory, a
function pointer was corrupted or pointing to a freed/data memory structure.
When a user pressed a key or moved the mouse, the user-input thread tried to
execute an event-handler callback, but the memory address for that handler
contained invalid data rather than executable code.
Common Causes in Apache Guacamole
Protocol Plugin Bugs (Most Common: RDP / FreeRDP):
Memory management issues (e.g., Use-After-Free) inside libguac-client-rdp,
libguac-client-vnc, or underlying C libraries like FreeRDP or libssh2
frequently cause input thread crashes.
Library Version Incompatibility:
A mismatch between the version of guacd and system dependencies (especially
FreeRDP 2.x vs 3.x).
Unexpected Input Formatting:
Passing an unhandled key code, unusual mouse/touch event, or clipboard sync
buffer overflow during user input processing.
----
> Unable to upgrade 1.5.5 to 1.6.0 due to sporadic hanging issue
> --------------------------------------------------------------
>
> Key: GUACAMOLE-2118
> URL: https://issues.apache.org/jira/browse/GUACAMOLE-2118
> Project: Guacamole
> Issue Type: Bug
> Affects Versions: 1.6.0
> Reporter: Jason Keltz
> Assignee: Mike Jumper
> Priority: Major
> Fix For: 1.6.1 [staging]
>
> Attachments: 2026-03-11_14-56.png, backtrace threads, backtrace.log,
> guacamole-logs.txt, guacd-178388-gdb.txt, guacd-178388-lsof.txt,
> guacd-240326-gdb.txt, guacd-240326-lsof.txt, guacd-stale-report.sh,
> image-2025-09-08-15-11-59-435.png, image-blocks.jpg
>
>
> I've been running Guacamole since around 2020, upgrading reasonably quickly
> each and every time there's been an update. I update my Tomcat to the latest
> 9.X release from time to time (currently 9.0.102) , and my JDK to the latest
> 8.X release from time to time (currently jdk8u452-b09).
> Recently, after attempting an upgrade from Guacamole 1.5.5 to 1.6.0, I ran
> into a problem. Initially, everything seemed to work just fine. I can
> connect to any of the systems I have available. However, at some point
> later, I notice in the tomcat logs a lot of "connects" and "disconnects" to
> hosts. Users start complaining that "Guacamole isn't working". What I
> noticed at this point was that when they would try to return to a connection,
> it would connect, and their existing connecting would start to redraw, but
> it would hang in the middle. If I restart guacd at this point, it starts to
> work again, but the problem comes back. Some users would see it. Other users
> were fine.
> I feel like there's a bug hiding, and it may require a lot of user activity
> to get to it. I ended up creating a devel system for testing, and I'm
> running guac 1.6.0 there, and I've enabled full debugging, but I can't seem
> to make it happen here yet. Is there any easy way I can force a bunch of
> connections? The devel system is running labtest Rocky 8.10 (RHEL8.10) with
> latest kernel and patches and this matches the production system. They are
> both installed with the same kickstart configuration.
> I'm opening this "bug" even though I don't have concrete information yet. If
> I really have to do it, I may have to re-install on the production system to
> get the debugging information that I need, but I'd rather not do it if not
> necessary since it causes user inconvenience, and Guacamole is an important
> part of our educational environment.
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