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  1. Core Server
  2. SERVER-41947

Disallow using the "system.views" collection name as the source or target names in the rename command

    • Minor Change
    • ALL
    • v4.2
    • Execution Team 2019-08-26, Execution Team 2019-09-09
    • 5

      This is a bug fix for a build failure where the following scenario leads to a deadlock:

      T1: Rename command is renaming 'test.coll' to 'test.system.views', so it has the MODE_IX on 'test' and MODE_X on both 'coll' and 'system.views'. The next step is to check if 'coll' is a view by calling the ViewCatalog::lookup() and waiting to acquire the ViewCatalog mutex which is currently held by T2.

      T2: Running CountCmd on a collection that didn't exist, but in AutoGetCollection we check if it could be a view and call ViewCatalog::lookup(), here we see that the ViewCatalog is invalidated, so we call _reloadIfNeeded. Now _reloadIfNeeded() uses the DurableViewCatalog::iterate but that requires the MODE_IS lock on the 'test.system.views' collection which is currently held by T1.

      So we have a deadlock where:
      T1 has MODE_X on 'test.system.views' but is waiting for ViewCatalog mutex.
      T2 has ViewCatalog mutex during reload and needs MODE_IS on 'test.system.views'.

            xiangyu.yao@mongodb.com Xiangyu Yao (Inactive)
            gregory.wlodarek@mongodb.com Gregory Wlodarek
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