Revert "MDEV-21452: Amend HEAD^"

This reverts commit d32ff4ff.
The code around suspending and resuming threads is rather convoluted.
In particular, que_thr_stop_for_mysql() and
lock_wait_suspend_thread() are separated from each other,
and the trx->mutex is being acquired and released multiple times
while a lock wait is being registered. Also, there are multiple
state fields related to lock waits, both in que_thr_t and trx_t.

storage/innobase/include/lock0priv.h

@@ -642,7 +642,6 @@ inline void lock_reset_lock_and_trx_wait(lock_t* lock)
 {
 	ut_ad(lock_get_wait(lock));
 	mysql_mutex_assert_owner(&lock_sys.mutex);
-	mysql_mutex_assert_owner(&lock->trx->mutex);
 	ut_ad(lock->trx->lock.wait_lock == NULL
 	      || lock->trx->lock.wait_lock == lock);
 	lock->trx->lock.wait_lock = NULL;

storage/innobase/lock/lock0lock.cc

@@ -2021,11 +2021,12 @@ static void lock_grant_after_reset(lock_t* lock)
 }
 
 /** Grant a lock to a waiting lock request and release the waiting transaction. */
-static void lock_grant(lock_t *lock)
+static void lock_grant(lock_t* lock)
 {
-  mysql_mutex_lock(&lock->trx->mutex);
-  lock_grant_have_trx_mutex(lock);
-  mysql_mutex_unlock(&lock->trx->mutex);
+	lock_reset_lock_and_trx_wait(lock);
+	mysql_mutex_lock(&lock->trx->mutex);
+	lock_grant_after_reset(lock);
+	mysql_mutex_unlock(&lock->trx->mutex);
 }
 
 /*************************************************************//**
@@ -2046,14 +2047,14 @@ lock_rec_cancel(
 	/* Reset the bit (there can be only one set bit) in the lock bitmap */
 	lock_rec_reset_nth_bit(lock, lock_rec_find_set_bit(lock));
 
-	mysql_mutex_lock(&lock->trx->mutex);
-
 	/* Reset the wait flag and the back pointer to lock in trx */
 
 	lock_reset_lock_and_trx_wait(lock);
 
 	/* The following function releases the trx from lock wait */
 
+	mysql_mutex_lock(&lock->trx->mutex);
+
 	thr = que_thr_end_lock_wait(lock->trx);
 
 	if (thr != NULL) {
@@ -2402,9 +2403,7 @@ lock_rec_move_low(
 		lock_rec_reset_nth_bit(lock, donator_heap_no);
 
 		if (type_mode & LOCK_WAIT) {
-			mysql_mutex_lock(&lock->trx->mutex);
 			lock_reset_lock_and_trx_wait(lock);
-			mysql_mutex_unlock(&lock->trx->mutex);
 		}
 
 		/* Note that we FIRST reset the bit, and then set the lock:
@@ -2521,9 +2520,8 @@ lock_move_reorganize_page(
 		lock_rec_bitmap_reset(lock);
 
 		if (lock_get_wait(lock)) {
-			mysql_mutex_lock(&lock->trx->mutex);
+
 			lock_reset_lock_and_trx_wait(lock);
-			mysql_mutex_unlock(&lock->trx->mutex);
 		}
 
 		lock = lock_rec_get_next_on_page(lock);
@@ -2699,9 +2697,7 @@ lock_move_rec_list_end(
 				ut_ad(!page_rec_is_metadata(orec));
 
 				if (type_mode & LOCK_WAIT) {
-					mysql_mutex_lock(&lock->trx->mutex);
 					lock_reset_lock_and_trx_wait(lock);
-					mysql_mutex_unlock(&lock->trx->mutex);
 				}
 
 				lock_rec_add_to_queue(
@@ -2799,9 +2795,7 @@ lock_move_rec_list_start(
 				ut_ad(!page_rec_is_metadata(prev));
 
 				if (type_mode & LOCK_WAIT) {
-					mysql_mutex_lock(&lock->trx->mutex);
 					lock_reset_lock_and_trx_wait(lock);
-					mysql_mutex_unlock(&lock->trx->mutex);
 				}
 
 				lock_rec_add_to_queue(
@@ -2897,9 +2891,7 @@ lock_rtr_move_rec_list(
 			if (rec1_heap_no < lock->un_member.rec_lock.n_bits
 			    && lock_rec_reset_nth_bit(lock, rec1_heap_no)) {
 				if (type_mode & LOCK_WAIT) {
-					mysql_mutex_lock(&lock->trx->mutex);
 					lock_reset_lock_and_trx_wait(lock);
-					mysql_mutex_unlock(&lock->trx->mutex);
 				}
 
 				lock_rec_add_to_queue(

storage/innobase/lock/lock0wait.cc

@@ -326,11 +326,11 @@ lock_wait_suspend_thread(
 		thd_wait_begin(trx->mysql_thd, THD_WAIT_TABLE_LOCK);
 	}
 
-	mysql_mutex_lock(&trx->mutex);
+	mysql_mutex_lock(&lock_sys.mutex);
 	while (trx->lock.wait_lock) {
-		mysql_cond_wait(&slot->cond, &trx->mutex);
+		mysql_cond_wait(&slot->cond, &lock_sys.mutex);
 	}
-	mysql_mutex_unlock(&trx->mutex);
+	mysql_mutex_unlock(&lock_sys.mutex);
 
 	thd_wait_end(trx->mysql_thd);