MDEV-33978 P_S.THREADS is not showing all server threads

page_encrypt_thread_key: The key for fil_crypt_thread().

All other InnoDB threads should already have been registered for
performance_schema ever since
commit a2f510fccf

storage/innobase/fil/fil0crypt.cc

@@ -80,6 +80,10 @@ static uint n_fil_crypt_iops_allocated = 0;
 
 #define DEBUG_KEYROTATION_THROTTLING 0
 
+#ifdef UNIV_PFS_THREAD
+mysql_pfs_key_t page_encrypt_thread_key;
+#endif /* UNIV_PFS_THREAD */
+
 /** Statistics variables */
 static fil_crypt_stat_t crypt_stat;
 static ib_mutex_t crypt_stat_mutex;
@@ -2145,6 +2149,10 @@ extern "C" UNIV_INTERN
 os_thread_ret_t
 DECLARE_THREAD(fil_crypt_thread)(void*)
 {
+	my_thread_init();
+#ifdef UNIV_PFS_THREAD
+	pfs_register_thread(page_encrypt_thread_key);
+#endif /* UNIV_PFS_THREAD */
 	mutex_enter(&fil_crypt_threads_mutex);
 	uint thread_no = srv_n_fil_crypt_threads_started;
 	srv_n_fil_crypt_threads_started++;
@@ -2242,6 +2250,7 @@ DECLARE_THREAD(fil_crypt_thread)(void*)
 	/* We count the number of threads in os_thread_exit(). A created
 	thread should always use that to exit and not use return() to exit. */
 
+	my_thread_end();
 	return os_thread_exit();
 }
 

storage/innobase/handler/ha_innodb.cc

@@ -579,6 +579,7 @@ performance schema instrumented if "UNIV_PFS_THREAD"
 is defined */
 static PSI_thread_info	all_innodb_threads[] = {
 	PSI_KEY(page_cleaner_thread),
+	PSI_KEY(page_encrypt_thread),
 	PSI_KEY(trx_rollback_clean_thread),
 	PSI_KEY(thread_pool_thread)
 };

storage/innobase/include/srv0srv.h

@@ -469,6 +469,7 @@ extern ulong srv_buf_dump_status_frequency;
 
 # ifdef UNIV_PFS_THREAD
 extern mysql_pfs_key_t	page_cleaner_thread_key;
+extern mysql_pfs_key_t	page_encrypt_thread_key;
 extern mysql_pfs_key_t	trx_rollback_clean_thread_key;
 extern mysql_pfs_key_t	thread_pool_thread_key;