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, 50 insertions, 11 deletions

diff --git a/sql/scheduler.h b/sql/scheduler.h
index e7916031a27..40f0e28bc2c 100644
--- a/sql/scheduler.h
+++ b/sql/scheduler.h
@@ -28,38 +28,77 @@ class THD;
 
 /* Functions used when manipulating threads */
 
-class scheduler_functions
+struct scheduler_functions
 {
-public:
   uint max_threads;
   bool (*init)(void);
   bool (*init_new_connection_thread)(void);
   void (*add_connection)(THD *thd);
+  void (*thd_wait_begin)(THD *thd, int wait_type);
+  void (*thd_wait_end)(THD *thd);
   void (*post_kill_notification)(THD *thd);
   bool (*end_thread)(THD *thd, bool cache_thread);
   void (*end)(void);
-  scheduler_functions();
 };
 
+
+/**
+  Scheduler types enumeration.
+
+  The default of --thread-handling is the first one in the
+  thread_handling_names array, this array has to be consistent with
+  the order in this array, so to change default one has to change the
+  first entry in this enum and the first entry in the
+  thread_handling_names array.
+
+  @note The last entry of the enumeration is also used to mark the
+  thread handling as dynamic. In this case the name of the thread
+  handling is fetched from the name of the plugin that implements it.
+*/
 enum scheduler_types
 {
   SCHEDULER_ONE_THREAD_PER_CONNECTION=0,
   SCHEDULER_NO_THREADS,
-  SCHEDULER_POOL_OF_THREADS
+  SCHEDULER_TYPES_COUNT
 };
 
-void one_thread_per_connection_scheduler(scheduler_functions* func);
-void one_thread_scheduler(scheduler_functions* func);
+void one_thread_per_connection_scheduler();
+void one_thread_scheduler();
 
 enum pool_command_op
 {
   NOT_IN_USE_OP= 0, NORMAL_OP= 1, CONNECT_OP, KILL_OP, DIE_OP
 };
 
-#define HAVE_POOL_OF_THREADS 0                  /* For easyer tests */
-#define pool_of_threads_scheduler(A) one_thread_per_connection_scheduler(A)
-
+/*
+ To be used for pool-of-threads (implemeneted differently on various OSs)
+*/
 class thd_scheduler
-{};
+{
+public:
+  /*
+    Thread instrumentation for the user job.
+    This member holds the instrumentation while the user job is not run
+    by a thread.
+
+    Note that this member is not conditionally declared
+    (ifdef HAVE_PSI_INTERFACE), because doing so will change the binary
+    layout of THD, which is exposed to plugin code that may be compiled
+    differently.
+  */
+  PSI_thread *m_psi;
+
+  void *data;                  /* scheduler-specific data structure */
+
+#  ifndef DBUG_OFF
+  char dbug_explain[512];
+  bool set_explain;
+#  endif
 
-#endif /* SCHEDULER_INCLUDED */
+  thd_scheduler();
+  ~thd_scheduler();
+};
+
+extern scheduler_functions *thread_scheduler;
+
+#endif