[PATCH for-6.0? 0/3] job: Add job_wait_unpaused() for block-job-complete

From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
	Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	John Snow <jsnow@redhat.com>,
	qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PATCH for-6.0? 0/3] job: Add job_wait_unpaused() for block-job-complete
Date: Thu,  8 Apr 2021 18:20:36 +0200	[thread overview]
Message-ID: <20210408162039.242670-1-mreitz@redhat.com> (raw)

Hi,

See patch 1 for a detailed explanation of the problem.

The gist is: Draining a READY job makes it transition to STANDBY, and
jobs on STANDBY cannot be completed.  Ending the drained section will
schedule the job (so it is then resumed), but not wait until it is
actually running again.

Therefore, it can happen that issuing block-job-complete fails when you
issue it right after some draining operation.

I tried to come up with an iotest reproducer, but in the end I only got
something that reproduced the issue like 2/10 times, and it required
heavy I/O, so it is nothing I would like to have as part of the iotests.
Instead, I opted for a unit test, which allows me to cheat a bit
(specifically, locking the job IO thread before ending the drained
section).

Max Reitz (3):
  job: Add job_wait_unpaused() for block-job-complete
  test-blockjob: Test job_wait_unpaused()
  iotests/041: block-job-complete on user-paused job

 include/qemu/job.h         |  15 ++++
 blockdev.c                 |   3 +
 job.c                      |  42 +++++++++++
 tests/unit/test-blockjob.c | 140 +++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/041     |  13 +++-
 5 files changed, 212 insertions(+), 1 deletion(-)

-- 
2.29.2