Bug#38522: 5 seconds delay when closing application using embedded server

                  
The problem here is that embedded server starts handle_thread manager 
thread  on mysql_library_init() does not stop it on mysql_library_end().
At shutdown, my_thread_global_end() waits for thread count to become 0,
but since we did not stop the thread it will give up after 5 seconds.
             
Solution is to move shutdown for handle_manager thread from kill_server()
(mysqld specific) to clean_up() that is used by both embedded and mysqld.
            
This patch also contains some refactorings - to avoid duplicate code,
start_handle_manager() and stop_handle_manager() functions are introduced.
Unused variables are eliminated. handle_manager does not rely on global
variable abort_loop anymore to stop (abort_loop is not set for embedded).
            
Note: Specifically on Windows and when using DBUG version of libmysqld, 
the complete solution requires removing obsolete code my_thread_init() 
from my_thread_var(). This has a side effect that a DBUG statement 
after my_thread_end() can cause thread counter to be incremented, and 
embedded will hang for some seconds. Or worse, my_thread_init() will 
crash if critical sections have been deleted by the global cleanup 
routine that runs in a different thread. 

This patch also fixes and revert prior changes for Bug#38293 
"Libmysqld crash in mysql_library_init if language file missing".

Root cause of the crash observed in Bug#38293  was bug in my_thread_init() 
described above




client/mysql.cc:
  sql_protocol_typelib is not exported from libmysqld
  (does not make sense either)
  thus excluded from embedded client
dbug/dbug.c:
  revert changes for Bug#38293
include/my_dbug.h:
  revert changes for Bug#38293
libmysql/libmysql.c:
  Removed DBUG_POP call, because when called after my_end(), will access
  THR_key_mysys that is already deleted. The result of pthread_get_specific
  is not predictable in this case and hence DBUG_POP can crash.
libmysqld/examples/CMakeLists.txt:
  Revert changes for Bug#38293.
libmysqld/lib_sql.cc:
  code to start handle manager is factored out into 
  start_handle_manager() function
libmysqld/libmysqld.def:
  Revert changes for Bug #38293
  Remove excessive exports from libmysqld, export what API documents.
mysys/my_thr_init.c:
  Remove windows-DLL-specific workaround for something (old code, no documentation for
  what specifically). The problem is that even after my_thread_end() is finished, 
  DBUG statement can initiate my_thread_init(). This does not happen anywhere else and 
  should not happen on  Windows either.
sql/mysql_priv.h:
  - new functions start_handle_manager() and stop_handle_manager()
  - move manager_thread_in_use  variable to sql_manager.cc and made
  it static
  - remove manager_status, as it is unused
sql/mysqld.cc:
  Code to start/stop handle_manager thread is factored out into start_handle_manager()

1 files changed, 41 insertions, 13 deletions

diff --git a/sql/sql_manager.cc b/sql/sql_manager.cc
index 171ab55145a..b082f65bfb9 100644
--- a/sql/sql_manager.cc
+++ b/sql/sql_manager.cc
@@ -23,8 +23,9 @@
 
 #include "mysql_priv.h"
 
-ulong volatile manager_status;
-bool volatile manager_thread_in_use;
+
+static bool volatile manager_thread_in_use;
+static bool abort_manager;
 
 pthread_t manager_thread;
 pthread_mutex_t LOCK_manager;
@@ -63,7 +64,6 @@ bool mysql_manager_submit(void (*action)())
 pthread_handler_t handle_manager(void *arg __attribute__((unused)))
 {
   int error = 0;
-  ulong status;
   struct timespec abstime;
   bool reset_flush_time = TRUE;
   struct handler_cb *cb= NULL;
@@ -72,7 +72,6 @@ pthread_handler_t handle_manager(void *arg __attribute__((unused)))
 
   pthread_detach_this_thread();
   manager_thread = pthread_self();
-  manager_status = 0;
   manager_thread_in_use = 1;
 
   for (;;)
@@ -87,16 +86,14 @@ pthread_handler_t handle_manager(void *arg __attribute__((unused)))
 	set_timespec(abstime, flush_time);
         reset_flush_time = FALSE;
       }
-      while (!manager_status && (!error || error == EINTR) && !abort_loop)
+      while ((!error || error == EINTR) && !abort_manager)
         error= pthread_cond_timedwait(&COND_manager, &LOCK_manager, &abstime);
     }
     else
     {
-      while (!manager_status && (!error || error == EINTR) && !abort_loop)
+      while ((!error || error == EINTR) && !abort_manager)
         error= pthread_cond_wait(&COND_manager, &LOCK_manager);
     }
-    status = manager_status;
-    manager_status = 0;
     if (cb == NULL)
     {
       cb= cb_list;
@@ -104,7 +101,7 @@ pthread_handler_t handle_manager(void *arg __attribute__((unused)))
     }
     pthread_mutex_unlock(&LOCK_manager);
 
-    if (abort_loop)
+    if (abort_manager)
       break;
 
     if (error == ETIMEDOUT || error == ETIME)
@@ -121,11 +118,42 @@ pthread_handler_t handle_manager(void *arg __attribute__((unused)))
       my_free((uchar*)cb, MYF(0));
       cb= next;
     }
-
-    if (status)
-      DBUG_PRINT("error", ("manager did not handle something: %lx", status));
   }
   manager_thread_in_use = 0;
+  DBUG_LEAVE; // Can't use DBUG_RETURN after my_thread_end
   my_thread_end();
-  DBUG_RETURN(NULL);
+  return (NULL);
 }
+
+
+/* Start handle manager thread */
+void start_handle_manager()
+{
+  DBUG_ENTER("start_handle_manager");
+  abort_manager = false;
+  if (flush_time && flush_time != ~(ulong) 0L)
+  {
+    pthread_t hThread;
+    if (pthread_create(&hThread,&connection_attrib,handle_manager,0))
+      sql_print_warning("Can't create handle_manager thread");
+  }
+  DBUG_VOID_RETURN;
+}
+
+
+/* Initiate shutdown of handle manager thread */
+void stop_handle_manager()
+{
+  DBUG_ENTER("stop_handle_manager");
+  abort_manager = true;
+  pthread_mutex_lock(&LOCK_manager);
+  if (manager_thread_in_use)
+  {
+    DBUG_PRINT("quit", ("initiate shutdown of handle manager thread: 0x%lx",
+                        (ulong)manager_thread));
+   pthread_cond_signal(&COND_manager);
+  }
+  pthread_mutex_unlock(&LOCK_manager);
+  DBUG_VOID_RETURN;
+}
+