MDEV-28313: Shrink rw_trx_hash_element_t::mutex

The element mutex is unnecessarily large. The PERFORMANCE_SCHEMA
instrumentation was not even enabled.

storage/innobase/handler/ha_innodb.cc

@@ -546,7 +546,6 @@ mysql_pfs_key_t	trx_sys_mutex_key;
 mysql_pfs_key_t	srv_threads_mutex_key;
 mysql_pfs_key_t	thread_mutex_key;
 mysql_pfs_key_t row_drop_list_mutex_key;
-mysql_pfs_key_t	rw_trx_hash_element_mutex_key;
 mysql_pfs_key_t	read_view_mutex_key;
 
 /* all_innodb_mutexes array contains mutexes that are

storage/innobase/include/trx0sys.h

@@ -40,7 +40,6 @@ Created 3/26/1996 Heikki Tuuri
 
 #ifdef UNIV_PFS_MUTEX
 extern mysql_pfs_key_t trx_sys_mutex_key;
-extern mysql_pfs_key_t rw_trx_hash_element_mutex_key;
 #endif
 
 /** Checks if a page address is the trx sys header page.
@@ -335,16 +334,14 @@ trx_t* current_trx();
 
 struct rw_trx_hash_element_t
 {
-  rw_trx_hash_element_t(): trx(0)
+  rw_trx_hash_element_t()
   {
-    mysql_mutex_init(rw_trx_hash_element_mutex_key, &mutex, nullptr);
+    memset(reinterpret_cast<void*>(this), 0, sizeof *this);
+    mutex.init();
   }
 
 
-  ~rw_trx_hash_element_t()
-  {
-    mysql_mutex_destroy(&mutex);
-  }
+  ~rw_trx_hash_element_t() { mutex.destroy(); }
 
 
   trx_id_t id; /* lf_hash_init() relies on this to be first in the struct */
@@ -357,7 +354,7 @@ struct rw_trx_hash_element_t
   */
   Atomic_counter<trx_id_t> no;
   trx_t *trx;
-  mysql_mutex_t mutex;
+  srw_mutex mutex;
 };
 
 
@@ -526,10 +523,10 @@ class rw_trx_hash_t
   static my_bool debug_iterator(rw_trx_hash_element_t *element,
                                 debug_iterator_arg<T> *arg)
   {
-    mysql_mutex_lock(&element->mutex);
+    element->mutex.wr_lock();
     if (element->trx)
       validate_element(element->trx);
-    mysql_mutex_unlock(&element->mutex);
+    element->mutex.wr_unlock();
     return arg->action(element, arg->argument);
   }
 #endif
@@ -631,7 +628,7 @@ class rw_trx_hash_t
                       sizeof(trx_id_t)));
     if (element)
     {
-      mysql_mutex_lock(&element->mutex);
+      element->mutex.wr_lock();
       lf_hash_search_unpin(pins);
       if ((trx= element->trx)) {
         DBUG_ASSERT(trx_id == trx->id);
@@ -652,7 +649,7 @@ class rw_trx_hash_t
             trx->reference();
         }
       }
-      mysql_mutex_unlock(&element->mutex);
+      element->mutex.wr_unlock();
     }
     if (!caller_trx)
       lf_hash_put_pins(pins);
@@ -686,9 +683,9 @@ class rw_trx_hash_t
   void erase(trx_t *trx)
   {
     ut_d(validate_element(trx));
-    mysql_mutex_lock(&trx->rw_trx_hash_element->mutex);
-    trx->rw_trx_hash_element->trx= 0;
-    mysql_mutex_unlock(&trx->rw_trx_hash_element->mutex);
+    trx->rw_trx_hash_element->mutex.wr_lock();
+    trx->rw_trx_hash_element->trx= nullptr;
+    trx->rw_trx_hash_element->mutex.wr_unlock();
     int res= lf_hash_delete(&hash, get_pins(trx),
                             reinterpret_cast<const void*>(&trx->id),
                             sizeof(trx_id_t));
@@ -722,12 +719,12 @@ class rw_trx_hash_t
     May return element with committed transaction. If caller doesn't like to
     see committed transactions, it has to skip those under element mutex:
 
-      mysql_mutex_lock(&element->mutex);
+      element->mutex.wr_lock();
       if (trx_t trx= element->trx)
       {
         // trx is protected against commit in this branch
       }
-      mysql_mutex_unlock(&element->mutex);
+      element->mutex.wr_unlock();
 
     May miss concurrently inserted transactions.
 
@@ -1180,11 +1177,11 @@ class trx_sys_t
   {
     if (element->id < *id)
     {
-      mysql_mutex_lock(&element->mutex);
+      element->mutex.wr_lock();
       /* We don't care about read-only transactions here. */
       if (element->trx && element->trx->rsegs.m_redo.rseg)
         *id= element->id;
-      mysql_mutex_unlock(&element->mutex);
+      element->mutex.wr_unlock();
     }
     return 0;
   }

storage/innobase/lock/lock0lock.cc

@@ -4868,7 +4868,7 @@ static void lock_rec_block_validate(const page_id_t page_id)
 static my_bool lock_validate_table_locks(rw_trx_hash_element_t *element, void*)
 {
   lock_sys.assert_locked();
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (element->trx)
   {
     check_trx_state(element->trx);
@@ -4878,7 +4878,7 @@ static my_bool lock_validate_table_locks(rw_trx_hash_element_t *element, void*)
       if (lock->is_table())
         lock_table_queue_validate(lock->un_member.tab_lock.table);
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   return 0;
 }
 
@@ -5075,7 +5075,7 @@ static my_bool lock_rec_other_trx_holds_expl_callback(
   rw_trx_hash_element_t *element,
   lock_rec_other_trx_holds_expl_arg *arg)
 {
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (element->trx)
   {
     element->trx->mutex_lock();
@@ -5091,7 +5091,7 @@ static my_bool lock_rec_other_trx_holds_expl_callback(
     ut_ad(!expl_lock || expl_lock->trx == &arg->impl_trx);
     element->trx->mutex_unlock();
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   return 0;
 }
 
@@ -5835,7 +5835,7 @@ static my_bool lock_table_locks_lookup(rw_trx_hash_element_t *element,
                                        const dict_table_t *table)
 {
   lock_sys.assert_locked();
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (element->trx)
   {
     element->trx->mutex_lock();
@@ -5859,7 +5859,7 @@ static my_bool lock_table_locks_lookup(rw_trx_hash_element_t *element,
     }
     element->trx->mutex_unlock();
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   return 0;
 }
 #endif /* UNIV_DEBUG */

storage/innobase/trx/trx0roll.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2017, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2016, 2021, MariaDB Corporation.
+Copyright (c) 2016, 2022, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -631,7 +631,7 @@ struct trx_roll_count_callback_arg
 static my_bool trx_roll_count_callback(rw_trx_hash_element_t *element,
                                        trx_roll_count_callback_arg *arg)
 {
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (trx_t *trx= element->trx)
   {
     if (trx->is_recovered && trx_state_eq(trx, TRX_STATE_ACTIVE))
@@ -640,7 +640,7 @@ static my_bool trx_roll_count_callback(rw_trx_hash_element_t *element,
       arg->n_rows+= trx->undo_no;
     }
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   return 0;
 }
 
@@ -678,7 +678,7 @@ void trx_roll_report_progress()
 static my_bool trx_rollback_recovered_callback(rw_trx_hash_element_t *element,
                                                std::vector<trx_t*> *trx_list)
 {
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (trx_t *trx= element->trx)
   {
     trx->mutex_lock();
@@ -686,7 +686,7 @@ static my_bool trx_rollback_recovered_callback(rw_trx_hash_element_t *element,
       trx_list->push_back(trx);
     trx->mutex_unlock();
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   return 0;
 }
 

storage/innobase/trx/trx0trx.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2021, MariaDB Corporation.
+Copyright (c) 2015, 2022, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -1914,7 +1914,7 @@ static my_bool trx_recover_for_mysql_callback(rw_trx_hash_element_t *element,
   trx_recover_for_mysql_callback_arg *arg)
 {
   DBUG_ASSERT(arg->len > 0);
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (trx_t *trx= element->trx)
   {
     /*
@@ -1940,7 +1940,7 @@ static my_bool trx_recover_for_mysql_callback(rw_trx_hash_element_t *element,
       }
     }
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   /* Do not terminate upon reaching arg->len; count all transactions */
   return false;
 }
@@ -1949,13 +1949,13 @@ static my_bool trx_recover_for_mysql_callback(rw_trx_hash_element_t *element,
 static my_bool trx_recover_reset_callback(rw_trx_hash_element_t *element,
   void*)
 {
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (trx_t *trx= element->trx)
   {
     if (trx_state_eq(trx, TRX_STATE_PREPARED_RECOVERED))
       trx->state= TRX_STATE_PREPARED;
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   return false;
 }
 
@@ -2004,7 +2004,7 @@ static my_bool trx_get_trx_by_xid_callback(rw_trx_hash_element_t *element,
   trx_get_trx_by_xid_callback_arg *arg)
 {
   my_bool found= 0;
-  mysql_mutex_lock(&element->mutex);
+  element->mutex.wr_lock();
   if (trx_t *trx= element->trx)
   {
     trx->mutex_lock();
@@ -2026,7 +2026,7 @@ static my_bool trx_get_trx_by_xid_callback(rw_trx_hash_element_t *element,
     }
     trx->mutex_unlock();
   }
-  mysql_mutex_unlock(&element->mutex);
+  element->mutex.wr_unlock();
   return found;
 }