Re: [libvirt] [PATCH 1/2] virCommandDoAsyncIO: Resolve race

With current implementation, virCommandWait unregister the stdio callback and finish reading itself. However, the eventloop may already have been in process of executing the callback in which case one obtain these obscure error messages, like: 2013-02-06 11:41:43.766+0000: 19078: warning : virEventPollRemoveHandle:183 : Ignoring invalid remove watch -1 2013-02-06 11:41:43.766+0000: 19078: warning : virFileClose:65 : Tried to close invalid fd 25 The solution is to introduce a mutex and condition to virCommand, and wait in virCommandWait for the eventloop to process all IOs. This, however, requires all callees to unlock all mutexes held, otherwise the eventloop may try to lock one of them and experience deadlock. If that's the case, we will never be woken up to unlock the problematic mutex. --- src/qemu/qemu_driver.c | 58 +++++++++++++++++++++++++--- src/qemu/qemu_migration.c | 15 +++++++- src/util/vircommand.c | 98 ++++++++++++++++++++++++++++++++++++----------- src/util/virfile.c | 4 ++ 4 files changed, 146 insertions(+), 29 deletions(-)