[MDEV-13125] Undocumented change: Core dumps can now be enabled dynamically Created: 2017-06-19  Updated: 2020-08-25  Resolved: 2017-06-26

Status: Closed
Project: MariaDB Server
Component/s: Server
Affects Version/s: None
Fix Version/s: N/A

Type: Bug Priority: Minor
Reporter: Michaël de groot Assignee: Sergei Golubchik
Resolution: Not a Bug Votes: 0
Labels: None

Issue Links:
Relates
relates to MDEV-11356 Option skip-core-file does not work Closed

 Description   

Hi,

In MariaDB 10.1.23 and 10.2.6, core dumps can be enabled by changing the process limit:

prlimit --core=unlimited: --pid `pidof mysqld`

In MariaDB 10.1.19 this required a restart.

Way to test:
1. Install the repository
2. Install 10.1.23
3. change the process limit
4. kill -SIGSEGV `pidof mysqld`
5. Observer there is a core dump

Do the same with MariaDB 10.1.19 and observe there is no core dump.

This change was undocumented but it is very useful desired behaviour. Please add this change to the release notes and/or find out what changed it.

 Comments   
Comment by Michaël de groot [ 2017-06-19 ]

I think this change may be caused by the same change that caused this bug.

Comment by Sergei Golubchik [ 2017-06-21 ]

Are you sure it was a change in the server? May be something in your environment?
If the server — in what version exactly did it occur?

Comment by Elena Stepanova [ 2017-06-25 ]

The change in behavior happened in 10.1.20 with this revision:

commit 76546a099c24a06ad89238f61435051a4663b112
 
Author: Sergei Golubchik <serg@mariadb.org>
 
Date:   Mon Dec 5 15:51:24 2016 +0100
 
 
 
    MDEV-10382 Using systemd, mariadb doesn't restart on crashes
 
    
    when crashing on a signal, don't exit(), but re-signal it, so that
 
    the caller could check WIFSIGNALED()

Assigning to serg to confirm it was intentional and will stick, as it does appear to be convenient.

Comment by Michaël de groot [ 2017-06-26 ]

Very convenient! Please make this change documented, serg

Comment by Sergei Golubchik [ 2017-06-26 ]

This was a side effect. The goal of the commit was to properly pass the killing signal information to the parent process. Apparently this fixed coredumps too.

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