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  1. MariaDB Server
  2. MDEV-24094

Race condition and hang in INFORMATION_SCHEMA.INNODB_TABLESPACES_ENCRYPTION

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      The reduction of fil_system.mutex contention introduced a race condition that can lead to a hang of the server when the view INFORMATION_SCHEMA.INNODB_TABLESPACES_ENCRYPTION is accessed. If space->is_stopping() starts to hold right after the check, then we would attempt to acquire fil_system.mutex while we are already holding it.

      The fix is simple (and also clarifies what this is about):

      diff --git a/storage/innobase/handler/i_s.cc b/storage/innobase/handler/i_s.cc
      index ecc0905de56..4c9098f9a86 100644
      --- a/storage/innobase/handler/i_s.cc
      +++ b/storage/innobase/handler/i_s.cc
      @@ -7055,8 +7055,7 @@ i_s_tablespaces_encryption_fill_table(
       	for (fil_space_t* space = UT_LIST_GET_FIRST(fil_system.space_list);
       	     space; space = UT_LIST_GET_NEXT(space_list, space)) {
       		if (space->purpose == FIL_TYPE_TABLESPACE
      -		    && !space->is_stopping()) {
      -			space->reacquire();
      +		    && space->acquire_if_not_stopped(true)) {
       			mutex_exit(&fil_system.mutex);
       			if (int err = i_s_dict_fill_tablespaces_encryption(
       				    thd, space, tables->table)) {
      

      To avoid the race condition, we must atomically check the is_stopping() flag while incrementing the reference count.

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            Assignee:
            marko Marko Mäkelä
            Reporter:
            marko Marko Mäkelä
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              Updated:
              Resolved:

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