Bug #103660 Sporadic crashes with signal 11
Submitted: 11 May 2021 14:18 Modified: 11 May 2021 14:26
Reporter: Sebastiano Degan Email Updates:
Status: Can't repeat Impact on me:
Category:MySQL Server Severity:S2 (Serious)
Version:5.6.51 OS:Debian (9)
Assigned to: CPU Architecture:x86

[11 May 2021 14:18] Sebastiano Degan
After an upgrade to mysql 5.6.51 (from 5.6.50) we have been experiencing crashes (5/6 a day) with the following stack:

05:49:21 UTC - mysqld got signal 11 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed, 
something is definitely wrong and this may fail.
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 127233 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.
Thread pointer: 0x559db57f59c0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 7f3374a66e98 thread_stack 0x40000
Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (7f332c3172b0): UPDATE nodi set internet_online='0'  where id='3734'
Connection ID (thread ID): 11518
The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.

The query seems always to point to the same table, but that table is also one of the most used so we are unsure whether that is the real problem.
We have already issued an ALTER TABLE nodi FORCE with no result.

How to repeat:
Any attempt to replicate the problem on a test instance failed.
At the moment we have no way to replicate this.

Suggested fix:
Downgrade to 5.6.50
[11 May 2021 14:26] MySQL Verification Team
Thank you for the bug report. For further process of this bug report we need a repeatable test case which you could comment and print here. Anyway I would you suggest to upgrade to new current versions since 5.6 is on EOL: