WL#5363: Thread Pool Service Interface

In order to allow thread schedulers to be dynamically loaded,
it is necessary to make the following changes to the server:

- Two new service interfaces

- Modifications to InnoDB to inform the thread scheduler of state changes.

- Changes to the VIO subsystem for checking if data is available on a socket.

- Elimination of remains of the old thread pool implementation.

The two new service interfaces introduces are:

my_thread_scheduler
  A service interface to register a thread
  scheduler.

thd_wait
  A service interface to inform thread scheduler
  that the thread is about to start waiting.

In addition, the patch adds code that:

- Add a call to thd_wait for table locks in mysys
  thd_lock.c by introducing a set function that
  can be used to set a callback to be used when
  waiting on a lock and resuming from waiting.

- Calling the mysys set function from the server
  to set the callbacks correctly.

1 files changed, 17 insertions, 34 deletions

diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index b35e2545a18..a61f2ccbc23 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -64,7 +64,9 @@
 #include "events.h"
 #include "sql_audit.h"
 #include "probes_mysql.h"
+#include "scheduler.h"
 #include "debug_sync.h"
+#include "sql_callback.h"
 
 #ifdef WITH_PERFSCHEMA_STORAGE_ENGINE
 #include "../storage/perfschema/pfs_server.h"
@@ -504,7 +506,7 @@ ulong slave_trans_retries;
 uint  slave_net_timeout;
 uint slave_exec_mode_options;
 ulonglong slave_type_conversions_options;
-ulong thread_cache_size=0, thread_pool_size= 0;
+ulong thread_cache_size=0;
 ulong binlog_cache_size=0;
 ulonglong  max_binlog_cache_size=0;
 ulong query_cache_size=0;
@@ -935,8 +937,6 @@ my_bool opt_enable_shared_memory;
 HANDLE smem_event_connect_request= 0;
 #endif
 
-scheduler_functions thread_scheduler;
-
 my_bool opt_use_ssl  = 0;
 char *opt_ssl_ca= NULL, *opt_ssl_capath= NULL, *opt_ssl_cert= NULL,
      *opt_ssl_cipher= NULL, *opt_ssl_key= NULL;
@@ -1125,7 +1125,8 @@ static void close_connections(void)
       continue;
 
     tmp->killed= THD::KILL_CONNECTION;
-    thread_scheduler.post_kill_notification(tmp);
+    MYSQL_CALLBACK(thread_scheduler, post_kill_notification, (tmp));
+    mysql_mutex_lock(&tmp->LOCK_thd_data);
     if (tmp->mysys_var)
     {
       tmp->mysys_var->abort=1;
@@ -1138,6 +1139,7 @@ static void close_connections(void)
       }
       mysql_mutex_unlock(&tmp->mysys_var->mutex);
     }
+    mysql_mutex_unlock(&tmp->LOCK_thd_data);
   }
   mysql_mutex_unlock(&LOCK_thread_count); // For unlink from list
 
@@ -1543,7 +1545,7 @@ void clean_up(bool print_message)
   if (print_message && my_default_lc_messages && server_start_time)
     sql_print_information(ER_DEFAULT(ER_SHUTDOWN_COMPLETE),my_progname);
   cleanup_errmsgs();
-  thread_scheduler.end();
+  MYSQL_CALLBACK(thread_scheduler, end, ());
   finish_client_errs();
   DBUG_PRINT("quit", ("Error messages freed"));
   /* Tell main we are ready */
@@ -1823,7 +1825,7 @@ static void network_init(void)
   DBUG_ENTER("network_init");
   LINT_INIT(ret);
 
-  if (thread_scheduler.init())
+  if (MYSQL_CALLBACK_ELSE(thread_scheduler, init, (), 0))
     unireg_abort(1);			/* purecov: inspected */
 
   set_ports();
@@ -2071,7 +2073,7 @@ extern "C" sig_handler end_thread_signal(int sig __attribute__((unused)))
   if (thd && ! thd->bootstrap)
   {
     statistic_increment(killed_threads, &LOCK_status);
-    thread_scheduler.end_thread(thd,0);		/* purecov: inspected */
+    MYSQL_CALLBACK(thread_scheduler, end_thread, (thd,0)); /* purecov: inspected */
   }
   DBUG_VOID_RETURN;				/* purecov: deadcode */
 }
@@ -2679,7 +2681,7 @@ and this may fail.\n\n");
           (ulong) dflt_key_cache->key_cache_mem_size);
   fprintf(stderr, "read_buffer_size=%ld\n", (long) global_system_variables.read_buff_size);
   fprintf(stderr, "max_used_connections=%lu\n", max_used_connections);
-  fprintf(stderr, "max_threads=%u\n", thread_scheduler.max_threads);
+  fprintf(stderr, "max_threads=%u\n", thread_scheduler->max_threads);
   fprintf(stderr, "thread_count=%u\n", thread_count);
   fprintf(stderr, "connection_count=%u\n", connection_count);
   fprintf(stderr, "It is possible that mysqld could use up to \n\
@@ -2687,7 +2689,7 @@ key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = %lu K\n\
 bytes of memory\n", ((ulong) dflt_key_cache->key_cache_mem_size +
 		     (global_system_variables.read_buff_size +
 		      global_system_variables.sortbuff_size) *
-		     thread_scheduler.max_threads +
+		     thread_scheduler->max_threads +
                      max_connections * sizeof(THD)) / 1024);
   fprintf(stderr, "Hope that's ok; if not, decrease some variables in the equation.\n\n");
 
@@ -2932,7 +2934,7 @@ pthread_handler_t signal_hand(void *arg __attribute__((unused)))
     This should actually be '+ max_number_of_slaves' instead of +10,
     but the +10 should be quite safe.
   */
-  init_thr_alarm(thread_scheduler.max_threads +
+  init_thr_alarm(thread_scheduler->max_threads +
 		 global_system_variables.max_insert_delayed_threads + 10);
   if (thd_lib_detected != THD_LIB_LT && (test_flags & TEST_SIGINT))
   {
@@ -4640,23 +4642,6 @@ int mysqld_main(int argc, char **argv)
   }
 #endif
 
-#ifdef	__WIN__
-  /*
-    Before performing any socket operation (like retrieving hostname
-    in init_common_variables we have to call WSAStartup
-  */
-  {
-    WSADATA WsaData;
-    if (SOCKET_ERROR == WSAStartup (0x0101, &WsaData))
-    {
-      /* errors are not read yet, so we use english text here */
-      my_message(ER_WSAS_FAILED, "WSAStartup Failed", MYF(0));
-      /* Not enough initializations for unireg_abort() */
-      return 1;
-    }
-  }
-#endif /* __WIN__ */
-
   if (init_common_variables())
     unireg_abort(1);				// Will do exit
 
@@ -5310,7 +5295,7 @@ static void create_new_thread(THD *thd)
 
   thread_count++;
 
-  thread_scheduler.add_connection(thd);
+  MYSQL_CALLBACK(thread_scheduler, add_connection, (thd));
 
   DBUG_VOID_RETURN;
 }
@@ -7633,14 +7618,12 @@ static int get_options(int *argc_ptr, char ***argv_ptr)
     return 1;
 
 #ifdef EMBEDDED_LIBRARY
-  one_thread_scheduler(&thread_scheduler);
+  one_thread_scheduler();
 #else
   if (thread_handling <= SCHEDULER_ONE_THREAD_PER_CONNECTION)
-    one_thread_per_connection_scheduler(&thread_scheduler);
-  else if (thread_handling == SCHEDULER_NO_THREADS)
-    one_thread_scheduler(&thread_scheduler);
-  else
-    pool_of_threads_scheduler(&thread_scheduler);  /* purecov: tested */
+    one_thread_per_connection_scheduler();
+  else                  /* thread_handling == SCHEDULER_NO_THREADS) */
+    one_thread_scheduler();
 #endif
 
   global_system_variables.engine_condition_pushdown=