1. 12 Sep, 2014 1 commit
    • Tejun Heo's avatar
      workqueue: apply __WQ_ORDERED to create_singlethread_workqueue() · e09c2c29
      Tejun Heo authored
      create_singlethread_workqueue() is a compat interface for single
      threaded workqueue which maps to ordered workqueue w/ rescuer in the
      current implementation.  create_singlethread_workqueue() currently
      implemented by invoking alloc_workqueue() w/ appropriate parameters.
      
      8719dcea ("workqueue: reject adjusting max_active or applying
      attrs to ordered workqueues") introduced __WQ_ORDERED to protect
      ordered workqueues against dynamic attribute changes which can break
      ordering guarantees but forgot to apply it to
      create_singlethread_workqueue().  This in itself is okay as nobody
      currently uses dynamic attribute change on workqueues created with
      create_singlethread_workqueue().
      
      However, 4c16bd32 ("workqueue: implement NUMA affinity for unbound
      workqueues") broke singlethreaded guarantee for ordered workqueues
      through allocating a separate pool_workqueue on each NUMA node by
      default.  A later change 8a2b7538 ("workqueue: fix ordered
      workqueues in NUMA setups") fixed it by allocating only one global
      pool_workqueue if __WQ_ORDERED is set.
      
      Combined, the __WQ_ORDERED omission in create_singlethread_workqueue()
      became critical breaking its single threadedness and ordering
      guarantee.
      
      Let's make create_singlethread_workqueue() wrap
      alloc_ordered_workqueue() instead so that it inherits __WQ_ORDERED and
      can implicitly track future ordered_workqueue changes.
      
      v2: I missed that __WQ_ORDERED now protects against pwq splitting
          across NUMA nodes and incorrectly described the patch as a
          nice-to-have fix to protect against future dynamic attribute
          usages.  Oleg pointed out that this is actually a critical
          breakage due to 8a2b7538 ("workqueue: fix ordered workqueues
          in NUMA setups").
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Reported-by: default avatarMike Anderson <mike.anderson@us.ibm.com>
      Cc: Oleg Nesterov <onestero@redhat.com>
      Cc: Gustavo Luiz Duarte <gduarte@redhat.com>
      Cc: Tomas Henzl <thenzl@redhat.com>
      Cc: stable@vger.kernel.org
      Fixes: 4c16bd32 ("workqueue: implement NUMA affinity for unbound workqueues")
      e09c2c29
  2. 16 Aug, 2014 39 commits