Suddenly MariaDB has started having issues on my CENTOS 7. I am getting ERROR "2013 (HY000): Lost connection to MySQL server during query" when i try to update a table via subquery such as : update table1 set sal=32 where prikey in (select id from table2 where....). The tables are myisam not innodb.

I checked with mysqlcheck and everything reported fine. I also saw threads regarding the cache but no good. This is quite scary to happen in production systems...

Thank you very much. Regards

Stack trace

[ERROR] 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.

To report this bug, see http://kb.askmonty.org/en/reporting-bugs

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.

Server version: 5.5.56-MariaDB
key_buffer_size=134217728
read_buffer_size=131072
max_used_connections=1
max_threads=153
thread_count=1
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 466711 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x5645e589bab0
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 = 0x7f053c0a3dc0 thread_stack 0x48000
/usr/libexec/mysqld(my_print_stacktrace+0x3d)[0x5645e290096d]
/usr/libexec/mysqld(handle_fatal_signal+0x515)[0x5645e2516285]
/lib64/libpthread.so.0(+0xf5e0)[0x7f0542d235e0]
/usr/libexec/mysqld(+0x396724)[0x5645e240a724]
/usr/libexec/mysqld(_Z20get_best_combinationP4JOIN+0x35b)[0x5645e2410dcb]
/usr/libexec/mysqld(+0x3b73b3)[0x5645e242b3b3]
/usr/libexec/mysqld(_ZN4JOIN8optimizeEv+0x675)[0x5645e242e625]
/usr/libexec/mysqld(_ZN13st_select_lex31optimize_unflattened_subqueriesEb+0xc8)[0x5645e23ddb18]
/usr/libexec/mysqld(Z12mysql_updateP3THDP10TABLE_LISTR4ListI4ItemES6_PS4_jP8st_ordery15enum_duplicatesbPySB+0x3f9)[0x5645e246f359]
/usr/libexec/mysqld(_Z21mysql_execute_commandP3THD+0x2de5)[0x5645e23e8815]
/usr/libexec/mysqld(_Z11mysql_parseP3THDPcjP12Parser_state+0x125)[0x5645e23ec8c5]
/usr/libexec/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0x1753)[0x5645e23ee923]
/usr/libexec/mysqld(_Z24do_handle_one_connectionP3THD+0x1c2)[0x5645e24a0632]
/usr/libexec/mysqld(handle_one_connection+0x4a)[0x5645e24a06da]
/lib64/libpthread.so.0(+0x7e25)[0x7f0542d1be25]
/lib64/libc.so.6(clone+0x6d)[0x7f054151934d]

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0x7f0510004c18): update...
Connection ID (thread ID): 1
Status: NOT_KILLED

Optimizer switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on,extended_keys=off

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.
180405 12:46:16 mysqld_safe Number of processes running now: 0
180405 12:46:16 mysqld_safe mysqld restarted
180405 12:46:16 [Note] /usr/libexec/mysqld (mysqld 5.5.56-MariaDB) starting as process 5586 ...
180405 12:46:16 InnoDB: The InnoDB memory heap is disabled
180405 12:46:16 InnoDB: Mutexes and rw_locks use GCC atomic builtins
180405 12:46:16 InnoDB: Compressed tables use zlib 1.2.7
180405 12:46:16 InnoDB: Using Linux native AIO
180405 12:46:16 InnoDB: Initializing buffer pool, size = 128.0M
180405 12:46:16 InnoDB: Completed initialization of buffer pool
180405 12:46:16 InnoDB: highest supported file format is Barracuda.
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
InnoDB: Restoring possible half-written data pages from the doublewrite buffer...
180405 12:46:16 InnoDB: Waiting for the background threads to start
180405 12:46:17 Percona XtraDB (http://www.percona.com) 5.5.52-MariaDB-38.3 started; log sequence number 4191004
180405 12:46:17 [Note] Plugin 'FEEDBACK' is disabled.
180405 12:46:17 [Note] Server socket created on IP: '0.0.0.0'.
180405 12:46:17 [Note] Event Scheduler: Loaded 0 events
180405 12:46:17 [Note] /usr/libexec/mysqld: ready for connections.
Version: '5.5.56-MariaDB' socket: '/var/lib/mysql/mysql.sock' port: 3306 MariaDB Serve