On 10/20/2016 06:20 PM, John Snow wrote:
Requires: [Qemu-devel] [PATCH 0/7] blockjobs: preliminary refactoring work, Pt 1 There are a few problems with transactional job completion right now. First, if jobs complete so quickly they complete before remaining jobs get a chance to join the transaction, the completion mode can leave well known state and the QLIST can get corrupted and the transactional jobs can complete in batches or phases instead of all together. Second, if two or more jobs defer to the main loop at roughly the same time, it's possible for one job's cleanup to directly invoke the other job's cleanup from within the same thread, leading to a situation that will deadlock the entire transaction. Thanks to Vladimir for pointing out these modes of failure. I have omitted the test for right now, but wanted to air the patches on-list. It makes no attempt to change the locking mechanisms around qmp_transaction right now, asserting instead that things are no more broken than they were, especially in the case of dataplane. I will make further attempts to clarify the locking mechanisms around qmp_transaction after Paolo's changes go in. ________________________________________________________________________________ For convenience, this branch is available at: https://github.com/jnsnow/qemu.git branch job-fix-race-condition https://github.com/jnsnow/qemu/tree/job-fix-race-condition This version is tagged job-fix-race-condition-v1: https://github.com/jnsnow/qemu/releases/tag/job-fix-race-condition-v1 John Snow (4): blockjob: add .clean property blockjob: add .start field blockjob: add block_job_start blockjob: refactor backup_start as backup_job_create Vladimir Sementsov-Ogievskiy (1): blockjob: fix dead pointer in txn list block/backup.c | 59 +++++++++++++++++-------------- block/commit.c | 4 +-- block/mirror.c | 5 +-- block/replication.c | 12 ++++--- block/stream.c | 4 +-- blockdev.c | 83 ++++++++++++++++++++++++++++---------------- blockjob.c | 55 ++++++++++++++++++++++------- include/block/block_int.h | 23 ++++++------ include/block/blockjob.h | 9 +++++ include/block/blockjob_int.h | 11 ++++++ tests/test-blockjob-txn.c | 12 +++---- 11 files changed, 182 insertions(+), 95 deletions(-)
My apologies, I mis-typed Vladimir's email in this series. Please include him in any replies.
