1. 04 Mar, 2008 5 commits
    • Michael Hanselmann's avatar
      Codestyle updates for locking code · cdb08f44
      Michael Hanselmann authored
      Reviewed-by: ultrotter
      cdb08f44
    • Guido Trotter's avatar
      LockSet: make acquire() able to get the whole set · 3b7ed473
      Guido Trotter authored
      This new functionality makes it possible to acquire a whole set, by passing
      "None" to the acquire() function as the list of elements. This will avoid new
      additions to the set, and then acquire all the current elements. The list of
      all elements acquired will be returned at the end.
      
      Deletions can still happen during the acquire process and we'll deal with it by
      just skipping the deleted elements: it's effectively as if they were deleted
      before we called the function. After we've finished though we hold all the
      elements, so no more deletes can be performed before we release them.
      
      Any call to release() will then first of all release the "set-level" lock if
      we're holding it, and then all or some of the locks we have.
      
      Some new tests checks that this feature works as intended.
      
      Reviewed-by: imsnah
      
      3b7ed473
    • Guido Trotter's avatar
      LockSet: improve remove() api · 3f404fc5
      Guido Trotter authored
      Lockset's remove() function used to return a list of locks we failed to remove.
      Rather than doing this we'll return a list of removed locks, so it's more
      similar to how acquire() behaves. This patch also fixes the relevant unit tests.
      
      Reviewed-by: imsnah
      
      3f404fc5
    • Guido Trotter's avatar
      LockSet: make acquire() return the set of names · 0cc00929
      Guido Trotter authored
      In a LockSet acquire() returned True on success. This code changes that to
      return a set containing the names of the elements acquired. This is still a
      true value if we acquired any lock but is slightly more useful (because if
      needed one has access to this data without querying for it). The only change
      happens if acquiring no locks, which though is a usage which should not
      normally happen because it has no practical use.
      
      The patch also changes a some tests to check that the new format is respected.
      
      Reviewed-by: imsnah
      
      0cc00929
    • Guido Trotter's avatar
      Initial GanetiLockManager implementation · 7ee7c0c7
      Guido Trotter authored
      Includes some locking-related constants and explanations on how the
      LockManager should be used, the class itself and its test cases.
      
      The class includes:
        - a basic constructor
        - functions to acquire and release lists of locks at the same level
        - functions to add and remove list of locks at modifiable levels
        - dynamic checks against out-of-order acquisitions and other illegal ops
      
      Its testing library checks that the LockManager behaves correctly and that the
      external assumptions it relies on are respected.
      
      Reviewed-by: imsnah
      7ee7c0c7
  2. 28 Feb, 2008 1 commit
    • Guido Trotter's avatar
      LockSet implementation and unit tests · aaae9bc0
      Guido Trotter authored
      A LockSet represents locking for a set of resources of the same type. A thread
      can acquire multiple resources at the same time, and release some or all of
      them, but cannot acquire more resources incrementally at different times
      without releasing all of them in between.
      
      Internally a LockSet uses a SharedLock for each resource to be able to grant
      both exclusive and shared acquisition. It also supports safe addition and
      removal of resources at runtime. Acquisitions are ordered alphabetically in
      order to grant them to be deadlock-free. A lot of assumptions about how the
      code interacts are made in order to grant both safety and speed; in order to
      document all of them the code features pretty lenghty comments.
      
      The test suit tries to catch most common interactions but cannot really tests
      tight race conditions, for which we still need to rely on human checking.
      
      This is the second basic building block for the Ganeti Lock Manager. Instance
      and Node locks will be put in LockSets to manage their acquisition and release.
      
      Reviewed-by: imsnah
      aaae9bc0
  3. 21 Feb, 2008 1 commit
    • Guido Trotter's avatar
      Add a few SharedLock delete() tests · 84152b96
      Guido Trotter authored
      - Check that even a shared acquire() fails on a deleted lock
      - Check that delete() fails on a lock you share (must own it or nothing)
      
      These are assumptions I build on in future code, so better check for them.
      Currently no code change is necessary for them to be valid.
      
      Reviewed-by: iustinp
      84152b96
  4. 20 Feb, 2008 1 commit
    • Guido Trotter's avatar
      SharedLock: fix a wrong unit-test helper code · 4354ab03
      Guido Trotter authored
      The _doItDelete helper code was supposed to be used to dispatch threads that
      deleted the SharedLock. It actually just acquired it exclusively. This remained
      unnoticed as the helper thread is just used to test interaction, not the delete
      code by itself, and delete requires an exclusive acquire anyway.
      
      Reviewed-by: imsnah
      4354ab03
  5. 19 Feb, 2008 1 commit
    • Guido Trotter's avatar
      Add the delete() operation to SharedLock · a95fd5d7
      Guido Trotter authored
      This new operation lets a lock be cleanly deleted. The lock will be exclusively
      held before deletion, and after it pending and future acquires will raise an
      exception. Other SharedLock operations are modify to deal with delete() and to
      avoid code duplication.
      
      This patch also adds unit testing for the new function and its interaction with
      the other lock features. The helper threads are sligtly modified to handle and
      report the condition of a deleted lock. As a bonus a non-related unit test
      about not supporting non-blocking mode yet has been added as well.
      
      This feature will be used by the LockSet in order to support deadlock-free
      delete of resources. This in turn will be useful to gracefully handle the
      removal of instances and nodes from the cluster dealing with the fact that
      other operations may be pending on them.
      
      Reviewed-by: iustinp
      a95fd5d7
  6. 18 Feb, 2008 1 commit
  7. 08 Feb, 2008 1 commit
    • Guido Trotter's avatar
      Shared Lock implementation and unit tests. · 162c1c1f
      Guido Trotter authored
      Adding a locking.py file for the ganeti locking library. Its first component is
      the implementation of a non-recursive blocking shared lock complete with a
      testing library.
      
      Reviewed-by: imsnah, iustinp
      162c1c1f