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[RFC PATCH v2 00/14] job: replace AioContext lock with job_mutex

From: Emanuele Giuseppe Esposito
Subject: [RFC PATCH v2 00/14] job: replace AioContext lock with job_mutex
Date: Thu, 4 Nov 2021 10:53:20 -0400

In this series, we want to remove the AioContext lock and instead
use the already existent job_mutex to protect the job structures
and list. This is part of the work to get rid of AioContext lock
usage in favour of smaller granularity locks.

In order to simplify reviewer's job, job lock/unlock functions and
macros are added as empty prototypes (nop) in patch 1.
They are converted to use the actual job mutex only in the last
patch, 14. In this way we can freely create locking sections
without worrying about deadlocks with the aiocontext lock.

Patch 2 defines what fields in the job structure need protection,
and patches 3-4 categorize respectively locked and unlocked
functions in the job API.

Patch 5-9 are in preparation to the job locks, they try to reduce
the aiocontext critical sections and other minor fixes.

Patch 10-13 introduces the (nop) job lock into the job API and
its users, following the comments and categorizations done in
patch 2-3-4.

Patch 14 makes the prototypes in patch 1 use the job_mutex and
removes all aiocontext lock at the same time.

Tested this series by running unit tests, qemu-iotests and qtests

This serie is based on my previous series "block layer: split
block APIs in global state and I/O".

Based-on: <20211025101735.2060852-1-eesposit@redhat.com>
RFC v2:
* mu(u)ltiple typos in commit messages
* job API split patches are sent separately in another series
* use of empty job_{lock/unlock} and JOB_LOCK_GUARD/WITH_JOB_LOCK_GUARD
  to avoid deadlocks and simplify the reviewer job

Emanuele Giuseppe Esposito (14):
  job.c: make job_lock/unlock public
  job.h: categorize fields in struct Job
  job.h: define locked functions
  job.h: define unlocked functions
  block/mirror.c: use of job helpers in drivers to avoid TOC/TOU
  job.c: make job_event_* functions static
  job.c: move inner aiocontext lock in callbacks
  aio-wait.h: introduce AIO_WAIT_WHILE_UNLOCKED
  jobs: remove aiocontext locks since the functions are under BQL
  jobs: protect jobs with job_lock/unlock
  block_job_query: remove atomic read
  jobs: use job locks and helpers also in the unit tests
  jobs: add job lock in find_* functions
  job.c: enable job lock/unlock and remove Aiocontext locks

 include/block/aio-wait.h         |  15 +-
 include/qemu/job.h               | 171 ++++++++++---
 block.c                          |   6 +
 block/mirror.c                   |   8 +-
 block/replication.c              |   6 +
 blockdev.c                       |  88 +++----
 blockjob.c                       |  62 +++--
 job-qmp.c                        |  54 ++--
 job.c                            | 410 ++++++++++++++++++++++---------
 monitor/qmp-cmds.c               |   2 +
 qemu-img.c                       |   8 +-
 tests/unit/test-bdrv-drain.c     |  44 ++--
 tests/unit/test-block-iothread.c |   6 +-
 tests/unit/test-blockjob-txn.c   |  10 +
 tests/unit/test-blockjob.c       |  68 ++---
 15 files changed, 628 insertions(+), 330 deletions(-)


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