The problem in MariaDB is introduced by this merge commit:
c33db2cdc0
The merge comes from mysql and the original author comes from this
commit from MySQL:
------------------------------------------------
commit 160b823d146288d66638e4a740d6d2da72f9a689
Author: Marc Alff <marc.alff@oracle.com>
Date: Tue Aug 30 12:14:07 2016 +0200
Bug#22551677 SIGNAL 11 IN LF_PINBOX_PUT_PINS
Backport to 5.6
------------------------------------------------
The breaking change is in start_socket_wait_v1 where instead of using
m_thread_owner, we make use of my_pthread_getspecific_ptr to fetch a
thread local storage value. Unfortunately this invalidates the
"m_thread_owner" member when a socket is created. The internals of the
socket structure have m_thread_owner set to NULL, but when checking for
ownership we actually look at the current thread's key store.
This seems incorrect however it is not immediately apparent why.
To not diverge from MySQL's reasoning as it is not described what the
actual problem was that this commit is trying to fix, I have adjusted the
unittest to account for this new behaviour. We destroy the current
thread in the unit test, such that the newly created socket actually has
no thread owner. The m_thread_owner is untouched in all this.
including the big commit
commit 305130361bf72726de220f3d2b2787395e10be61
Author: Marc Alff <marc.alff@oracle.com>
Date: Tue Feb 10 11:31:32 2015 +0100
WL#8354 BACKPORT DIGEST IMPROVEMENTS TO MYSQL 5.6
(with the following commits) and related changes in sql/
Performance schema tables are local to a server and they should not
be allowed to be executed by the slave from the relay log.
From 5.6.10, P_S events are not written into the binary log.
But prior to that, from mysql 5.5 onwards, P_S events are written
to the binary log by master.
The following are problematic scenarios:
1. Master 5.5 -> Slave 5.5
========================
A) RBR: Slave crashes
B) SBR: P_S statements are replicated.
2.Master 5.5 -> Slave 5.6
========================
A) RBR: SQL thd generates error
B) SBR : P_S statements are replicated
3. 5.5 binlog executed on a server 5.5 using mysqlbinlog|mysql
=================================================================
A) RBR: Server crash (because of BINLOG'... statement)
B) SBR: P_S statements are executed
4. 5.5 binlog executed on server 5.6 using mysqlbinlog|mysql
================================================================
A) RBR: SQL error (because of BINLOG'... statement)
B) SBR: P_S statements are executed.
The generalized behaviour should be:
a) Slave SQL thread should certainly ignore P_S events read from
the relay log.
b) mysqlbinlog|mysql should replay the binlog succesfully.
DESTRUCTED THD OBJ
Prior to fix, function check_performance_schema() could leave
behind stale pointers in thread local storage, for the following keys:
- THR_THD (used by _current_thd)
- THR_MALLOC (used for memory allocation)
This is an unsafe practice, which can potentially cause crashes,
and that can cause other bugs when code is modified during maintenance.
With this fix, thread local storage keys used temporarily within
function check_performance_schema() are cleaned up after use.
