(gdb) bt full

#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185

No locals.

#1  0x0000564a97d3105b in inline_mysql_cond_wait (src_file=0x564a98383b88 "/home/hartmut/projects/mariadb/releases/mariadb-10.2.1/sql/mysqld.cc", src_line=6324, 

    mutex=0x564a98b87240 <LOCK_thread_count>, that=0x564a98b86b40 <COND_thread_count>)

    at /home/hartmut/projects/mariadb/releases/mariadb-10.2.1/include/mysql/psi/mysql_thread.h:1149

        result = <optimized out>

#2  bootstrap (file=<optimized out>) at /home/hartmut/projects/mariadb/releases/mariadb-10.2.1/sql/mysqld.cc:6324

        thd = <optimized out>

        error = -512

#3  0x0000564a97d3ac37 in mysqld_main (argc=14, argv=0x7f5e87c7c4e8) at /home/hartmut/projects/mariadb/releases/mariadb-10.2.1/sql/mysqld.cc:5965

        ho_error = <optimized out>

        new_thread_stack_size = <optimized out>

#4  0x00007f5e88fac830 in __libc_start_main (main=0x564a97d1cc10 <main(int, char**)>, argc=11, argv=0x7fff6b209d38, init=<optimized out>, fini=<optimized out>, 

    rtld_fini=<optimized out>, stack_end=0x7fff6b209d28) at ../csu/libc-start.c:291

        result = <optimized out>

        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, -5463114453628400794, 94878374749760, 140734990687536, 0, 0, -1782026426318501018, -1871456903574500506}, 

              mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x7fff6b209d98, 0x7f5e8b619168}, data = {prev = 0x0, cleanup = 0x0, canceltype = 1797299608}}}

        not_first_call = <optimized out>

#5  0x0000564a97d2e669 in _start ()

commit 562c1df7d97cb23145e09b3482fd18d49476752d

Author: Sergei Golubchik <serg@mariadb.org>

Date:   Sat May 14 13:22:47 2016 +0200

    cleanup: thread_count

    move thread_count handling into THD:

    * increment thread_count in THD constructor

    * decrement thread_count in THD destructor

    * never modify thread_count directly!

mysqld: /data/src/10.2/sql/sql_parse.cc:1086: void do_handle_bootstrap(THD*): Assertion `thread_count == 0' failed.

160816  2:25:38 [ERROR] mysqld got signal 6 ;

#6  0x00007f23bb5cf266 in __assert_fail_base (fmt=0x7f23bb708238 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=assertion@entry=0x7f23be7353a2 "thread_count == 0", file=file@entry=0x7f23be735278 "/data/src/10.2/sql/sql_parse.cc", line=line@entry=1086, function=function@entry=0x7f23be736ed0 <do_handle_bootstrap(THD*)::__PRETTY_FUNCTION__> "void do_handle_bootstrap(THD*)") at assert.c:92

#7  0x00007f23bb5cf312 in __GI___assert_fail (assertion=0x7f23be7353a2 "thread_count == 0", file=0x7f23be735278 "/data/src/10.2/sql/sql_parse.cc", line=1086, function=0x7f23be736ed0 <do_handle_bootstrap(THD*)::__PRETTY_FUNCTION__> "void do_handle_bootstrap(THD*)") at assert.c:101

#8  0x00007f23bde073c9 in do_handle_bootstrap (thd=0x7f2397bbd070) at /data/src/10.2/sql/sql_parse.cc:1086

#9  0x00007f23bde072fd in handle_bootstrap (arg=0x7f2397bbd070) at /data/src/10.2/sql/sql_parse.cc:1062

#10 0x00007f23bd4d10a4 in start_thread (arg=0x7f23bed20300) at pthread_create.c:309

#11 0x00007f23bb68987d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

commit 1cae1af6f9286ca6695206ce20c63bb639c60310

Author: Sergei Golubchik <serg@mariadb.org>

Date:   Mon Nov 7 22:35:02 2016 +0100

    MDEV-5800 InnoDB support for indexed vcols

      * remove old 5.2+ InnoDB support for virtual columns

      * enable corresponding parts of the innodb-5.7 sources

      * copy corresponding test cases from 5.7

      * copy detailed Alter_inplace_info::HA_ALTER_FLAGS flags from 5.7

         - and more detailed detection of changes in fill_alter_inplace_info()

      * more "innodb compatibility hooks" in sql_class.cc to

         - create/destroy/reset a THD (used by background purge threads)

         - find a prelocked table by name

         - open a table (from a background purge thread)

      * different from 5.7:

        - new service thread "thd_destructor_proxy" to make sure all THDs are

          destroyed at the correct point in time during the server shutdown

        - proper opening/closing of tables for vcol evaluations in

           + FK checks (use already opened prelocked tables)

           + purge threads (open the table, MDLock it, add it to tdc, close

             when not needed)

        - cache open tables in vc_templ

        - avoid unnecessary allocations, reuse table->record[0] and table->s->default_values

        - not needed in 5.7, because it overcalculates:

          + tell the server to calculate vcols for an on-going inline ADD INDEX

          + calculate vcols for correct error messages

      * update other engines (mroonga/tokudb) accordingly

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc

index d80706e..6dc9192 100644

--- a/sql/sql_parse.cc

+++ b/sql/sql_parse.cc

@@ -1085,20 +1085,11 @@ void do_handle_bootstrap(THD *thd)

 end:

   in_bootstrap= FALSE;

   delete thd;

-  if (!opt_bootstrap)

-  {

-    /*

-      We need to wake up main thread in case of read_init_file().

-      This is not done by THD::~THD() when there are other threads running

-      (binlog background thread, for example). So do it here again.

-    */

-    mysql_mutex_lock(&LOCK_thread_count);

-    mysql_cond_broadcast(&COND_thread_count);

-    mysql_mutex_unlock(&LOCK_thread_count);

-  }

+  mysql_mutex_lock(&LOCK_thread_count);

+  mysql_cond_broadcast(&COND_thread_count);

+  mysql_mutex_unlock(&LOCK_thread_count);

 #ifndef EMBEDDED_LIBRARY

-  DBUG_ASSERT(!opt_bootstrap || thread_count == 0);

   my_thread_end();

   pthread_exit(0);

 #endif