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  1. MariaDB Server
  2. MDEV-10365

Race condition in error handling of INSERT DELAYED

    Details

    • Sprint:
      5.5.51 & 10.2.2

      Description

      This race condition is hard to reproduce with unmodified code. But it is easily reproducible with error simulation as in the following patch:

      diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
      index c60ef6f..d10dc3d 100644
      --- a/sql/sql_insert.cc
      +++ b/sql/sql_insert.cc
      @@ -3021,7 +3021,7 @@ bool Delayed_insert::handle_inserts(void)
         table->use_all_columns();
       
         thd_proc_info(&thd, "upgrading lock");
      -  if (thr_upgrade_write_delay_lock(*thd.lock->locks, delayed_lock,
      +  if (1 || thr_upgrade_write_delay_lock(*thd.lock->locks, delayed_lock,
                                          thd.variables.lock_wait_timeout))
         {
           /*
      

      MTR test case:

      CREATE TABLE t1(a INT);
      let $i= 10000;
      disable_query_log;
      while ($i)
      {
        --error 0,1150
        INSERT DELAYED INTO t1 VALUES(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12),(13),(14),(15),(16),(17),(18),(19),(20);
        dec $i;
      }
      enable_query_log;
      DROP TABLE t1;
      

      Running this test makes threads stuck as following:

      +------+---------+-----------+------+---------+------+----------------------------+------------------------------------------------------------------------------------------------------+----------+
      | Id   | User    | Host      | db   | Command | Time | State                      | Info                                                                                                 | Progress |
      +------+---------+-----------+------+---------+------+----------------------------+------------------------------------------------------------------------------------------------------+----------+
      |    2 | root    | localhost | test | Query   |  261 | waiting for handler insert | INSERT DELAYED INTO t1 VALUES(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12),(13),(14),(15),(16), |    0.000 |
      | 5026 | root    | localhost | NULL | Query   |    0 | NULL                       | show processlist                                                                                     |    0.000 |
      | 8018 | DELAYED | localhost | test | Killed  |  263 | upgrading lock             |                                                                                                      |    0.000 |
      | 8025 | DELAYED | localhost | test | Killed  |  263 | upgrading lock             |                                                                                                      |    0.000 |
      | 8028 | DELAYED | localhost | test | Killed  |  263 | upgrading lock             |                                                                                                      |    0.000 |
      | 8029 | DELAYED | localhost | test | Killed  |  263 | upgrading lock             |                                                                                                      |    0.000 |
      | 8043 | DELAYED | localhost | test | Killed  |  263 | upgrading lock             |                                                                                                      |    0.000 |
      | 8056 | DELAYED | localhost | test | Killed  |  263 | upgrading lock             |                                                                                                      |    0.000 |
      | 8150 | DELAYED | localhost | test | Killed  |  263 | upgrading lock             |                                                                                                      |    0.000 |
      | 8170 | DELAYED | localhost | test | Killed  |  262 | upgrading lock             |                                                                                                      |    0.000 |
      | 8207 | DELAYED | localhost | test | Killed  |  262 | upgrading lock             |                                                                                                      |    0.000 |
      | 8243 | DELAYED | localhost | test | Killed  |  262 | upgrading lock             |                                                                                                      |    0.000 |
      | 8295 | DELAYED | localhost | test | Killed  |  261 | upgrading lock             |                                                                                                      |    0.000 |
      | 8305 | DELAYED | localhost | test | Killed  |  261 | upgrading lock             |                                                                                                      |    0.000 |
      +------+---------+-----------+------+---------+------+----------------------------+------------------------------------------------------------------------------------------------------+----------+
      

      The following patch makes it work:

      diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
      index c60ef6f..d10dc3d 100644
      --- a/sql/sql_insert.cc
      +++ b/sql/sql_insert.cc
      @@ -3238,6 +3238,7 @@ bool Delayed_insert::handle_inserts(void)
         max_rows= 0;                                  // For DBUG output
       #endif
         /* Remove all not used rows */
      +  mysql_mutex_lock(&mutex);
         while ((row=rows.get()))
         {
           if (table->s->blob_fields)
      @@ -3254,7 +3255,6 @@ bool Delayed_insert::handle_inserts(void)
         }
         DBUG_PRINT("error", ("dropped %lu rows after an error", max_rows));
         thread_safe_increment(delayed_insert_errors, &LOCK_delayed_status);
      -  mysql_mutex_lock(&mutex);
         DBUG_RETURN(1);
       }
       #endif /* EMBEDDED_LIBRARY */
      

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            • Assignee:
              svoj Sergey Vojtovich
              Reporter:
              svoj Sergey Vojtovich
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              • Created:
                Updated:
                Resolved: