diff --git a/mysql-test/suite/rpl/r/rpl_start_slave_deadlock_sys_vars.result b/mysql-test/suite/rpl/r/rpl_start_slave_deadlock_sys_vars.result
new file mode 100644
index 0000000..f69a323
--- /dev/null
+++ b/mysql-test/suite/rpl/r/rpl_start_slave_deadlock_sys_vars.result
@@ -0,0 +1,31 @@
+include/master-slave.inc
+[connection master]
+# connection: slave
+SET @save_slave_net_timeout = @@GLOBAL.slave_net_timeout;
+STOP SLAVE;
+include/wait_for_slave_to_stop.inc
+# open an extra connection to the slave
+# connection: slave2
+# set debug synchronization point
+SET DEBUG_SYNC='fix_slave_net_timeout SIGNAL parked WAIT_FOR go';
+# attempt to set slave_net_timeout, will wait on sync point
+SET @@GLOBAL.slave_net_timeout = 100;
+# connection: slave
+SET DEBUG_SYNC='now WAIT_FOR parked';
+# connection: slave1
+# attempt to start the SQL thread
+START SLAVE SQL_THREAD;
+# connection: slave
+# wait until SQL thread has been started
+# sleep a bit so that the SQL thread THD handle is initialized
+# signal the set slave_net_timeout to continue
+SET DEBUG_SYNC='now SIGNAL go';
+# connection: slave2
+# reap result of set slave_net_timeout
+# connection: slave1
+# reap result of starting the SQL thread
+# disconnect: slave2
+# connection: slave
+# cleanup
+SET @@GLOBAL.slave_net_timeout = @save_slave_net_timeout;
+include/rpl_end.inc
diff --git a/mysql-test/suite/rpl/t/rpl_start_slave_deadlock_sys_vars.test b/mysql-test/suite/rpl/t/rpl_start_slave_deadlock_sys_vars.test
new file mode 100644
index 0000000..dfcec67
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_start_slave_deadlock_sys_vars.test
@@ -0,0 +1,57 @@
+source include/master-slave.inc;
+source include/have_debug_sync.inc;
+
+--echo # connection: slave
+connection slave;
+SET @save_slave_net_timeout = @@GLOBAL.slave_net_timeout;
+STOP SLAVE;
+source include/wait_for_slave_to_stop.inc;
+
+--echo # open an extra connection to the slave
+connect(slave2,127.0.0.1,root,,test,$SLAVE_MYPORT,);
+--echo # connection: slave2
+--echo # set debug synchronization point
+SET DEBUG_SYNC='fix_slave_net_timeout SIGNAL parked WAIT_FOR go';
+--echo # attempt to set slave_net_timeout, will wait on sync point
+--send SET @@GLOBAL.slave_net_timeout = 100
+
+--echo # connection: slave
+connection slave;
+SET DEBUG_SYNC='now WAIT_FOR parked';
+
+--echo # connection: slave1
+connection slave1;
+--echo # attempt to start the SQL thread
+--send START SLAVE SQL_THREAD
+
+--echo # connection: slave
+connection slave;
+--echo # wait until SQL thread has been started
+let $wait_condition=
+  select count(*) = 1 from information_schema.processlist
+  where state = "Waiting for slave thread to start" and info = "START SLAVE SQL_THREAD";
+--source include/wait_condition.inc
+--echo # sleep a bit so that the SQL thread THD handle is initialized
+sleep 2;
+--echo # signal the set slave_net_timeout to continue
+SET DEBUG_SYNC='now SIGNAL go';
+
+--echo # connection: slave2
+connection slave2;
+--echo # reap result of set slave_net_timeout
+--reap
+
+--echo # connection: slave1
+connection slave1;
+--echo # reap result of starting the SQL thread
+--reap
+
+--echo # disconnect: slave2
+disconnect slave2;
+
+--echo # connection: slave
+connection slave;
+--echo # cleanup
+SET @@GLOBAL.slave_net_timeout = @save_slave_net_timeout;
+
+source include/rpl_end.inc;
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index f30fafb..4d58589 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -44,6 +44,7 @@
                      // mysql_user_table_is_in_short_password_format
 #include "derror.h"  // read_texts
 #include "sql_base.h"                           // close_cached_tables
+#include "debug_sync.h"                         // DEBUG_SYNC
 
 #ifdef WITH_PERFSCHEMA_STORAGE_ENGINE
 #include "../storage/perfschema/pfs_server.h"
@@ -3276,6 +3277,9 @@ static Sys_var_charptr Sys_slave_load_tmpdir(
 
 static bool fix_slave_net_timeout(sys_var *self, THD *thd, enum_var_type type)
 {
+  DEBUG_SYNC(thd, "fix_slave_net_timeout");
+
+  mysql_mutex_unlock(&LOCK_global_system_variables);
   mysql_mutex_lock(&LOCK_active_mi);
   DBUG_PRINT("info", ("slave_net_timeout=%u mi->heartbeat_period=%.3f",
                      slave_net_timeout,
@@ -3285,6 +3289,7 @@ static bool fix_slave_net_timeout(sys_var *self, THD *thd, enum_var_type type)
                         ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE_MAX,
                         ER(ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE_MAX));
   mysql_mutex_unlock(&LOCK_active_mi);
+  mysql_mutex_lock(&LOCK_global_system_variables);
   return false;
 }
 static Sys_var_uint Sys_slave_net_timeout(
@@ -3311,6 +3316,7 @@ static bool check_slave_skip_counter(sys_var *self, THD *thd, set_var *var)
 }
 static bool fix_slave_skip_counter(sys_var *self, THD *thd, enum_var_type type)
 {
+  mysql_mutex_unlock(&LOCK_global_system_variables);
   mysql_mutex_lock(&LOCK_active_mi);
   mysql_mutex_lock(&active_mi->rli.run_lock);
   /*
@@ -3326,6 +3332,7 @@ static bool fix_slave_skip_counter(sys_var *self, THD *thd, enum_var_type type)
   }
   mysql_mutex_unlock(&active_mi->rli.run_lock);
   mysql_mutex_unlock(&LOCK_active_mi);
+  mysql_mutex_lock(&LOCK_global_system_variables);
   return 0;
 }
 static Sys_var_uint Sys_slave_skip_counter(