commit ec8257231e81351c73227da46c2352847c417363
Author: Robert Golebiowski <robert.golebiowski@percona.com>
Date:   Thu Feb 22 08:57:18 2018 +0100

    Fix bug 89607 / PS-311 (On server shutdown threadpool is crashing in debug mode due to race condition)
    
    This patch was ported from 5.7. The original commit message from 5.7
    reads:
    "Moved calling set_my_sys_thread_var before signaling conditional
     variable THR_COND_threads. This is variable on which my_thread_global_end is
     waiting. After it is signalled THR_KEY_mysys_initialized is set to FALSE in
     my_thread_global_end. There is a debug assertion that THE_KEY_mysys_initialized == TRUE in
     set_my_sys_thread_var.
    
     Moved my_init_signals, which sets signal mask to block all
     handleable kill signals - which are later serviced by signal_hand thread. my_init_singals
     was moved before PFS initialization. PFS thread can be affected by
     "handleable kill" signals unless they have singal mask set.
    
    Only second part of this patch is ported from 5.7.
    The first part is no longer valid as the debug assertion
    THE_KEY_mysys_initialized == TRUE was removed.

diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 474a17a230b..a3613bd7a4d 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -5489,6 +5489,8 @@ int mysqld_main(int argc, char **argv)
   ulong requested_open_files;
   init_error_log();
   adjust_related_options(&requested_open_files);
+  // moved signal initialization here so that PFS thread inherited signal mask
+  my_init_signals();
 
 #ifdef WITH_PERFSCHEMA_STORAGE_ENGINE
   if (ho_error == 0) {
@@ -5718,8 +5720,6 @@ int mysqld_main(int argc, char **argv)
 
   if (init_common_variables()) unireg_abort(MYSQLD_ABORT_EXIT);  // Will do exit
 
-  my_init_signals();
-
   size_t guardize = 0;
 #ifndef _WIN32
   int retval = pthread_attr_getguardsize(&connection_attrib, &guardize);