tree c1ccc27a2148e1173950d276838803bc5fafcec8
parent c2e50e3d11a0bf4c973cc30478c1af0f2d5f8e81
author Stefan Hajnoczi <stefanha@redhat.com> 1405435466 +0200
committer Kevin Wolf <kwolf@redhat.com> 1408108034 +0200

thread-pool: avoid deadlock in nested aio_poll() calls

The thread pool has a race condition if two elements complete before
thread_pool_completion_bh() runs:

  If element A's callback waits for element B using aio_poll() it will
  deadlock since pool->completion_bh is not marked scheduled when the
  nested aio_poll() runs.

Fix this by marking the BH scheduled while thread_pool_completion_bh()
is executing.  This way any nested aio_poll() loops will enter
thread_pool_completion_bh() and complete the remaining elements.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>