[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-block] [PULL v2 04/10] jobs: add exit shim
From: |
Max Reitz |
Subject: |
[Qemu-block] [PULL v2 04/10] jobs: add exit shim |
Date: |
Fri, 31 Aug 2018 16:32:35 +0200 |
From: John Snow <address@hidden>
All jobs do the same thing when they leave their running loop:
- Store the return code in a structure
- wait to receive this structure in the main thread
- signal job completion via job_completed
Few jobs do anything beyond exactly this. Consolidate this exit
logic for a net reduction in SLOC.
More seriously, when we utilize job_defer_to_main_loop_bh to call
a function that calls job_completed, job_finalize_single will run
in a context where it has recursively taken the aio_context lock,
which can cause hangs if it puts down a reference that causes a flush.
You can observe this in practice by looking at mirror_exit's careful
placement of job_completed and bdrv_unref calls.
If we centralize job exiting, we can signal job completion from outside
of the aio_context, which should allow for job cleanup code to run with
only one lock, which makes cleanup callbacks less tricky to write.
Signed-off-by: John Snow <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Message-id: address@hidden
Reviewed-by: Jeff Cody <address@hidden>
Signed-off-by: Max Reitz <address@hidden>
---
include/qemu/job.h | 11 +++++++++++
job.c | 18 ++++++++++++++++++
2 files changed, 29 insertions(+)
diff --git a/include/qemu/job.h b/include/qemu/job.h
index e0e99870a1..1144d671a1 100644
--- a/include/qemu/job.h
+++ b/include/qemu/job.h
@@ -208,6 +208,17 @@ struct JobDriver {
*/
void (*drain)(Job *job);
+ /**
+ * If the callback is not NULL, exit will be invoked from the main thread
+ * when the job's coroutine has finished, but before transactional
+ * convergence; before @prepare or @abort.
+ *
+ * FIXME TODO: This callback is only temporary to transition remaining jobs
+ * to prepare/commit/abort/clean callbacks and will be removed before 3.1.
+ * is released.
+ */
+ void (*exit)(Job *job);
+
/**
* If the callback is not NULL, prepare will be invoked when all the jobs
* belonging to the same transaction complete; or upon this job's
completion
diff --git a/job.c b/job.c
index 7b3721d2c7..5df7791ad8 100644
--- a/job.c
+++ b/job.c
@@ -535,6 +535,18 @@ void job_drain(Job *job)
}
}
+static void job_exit(void *opaque)
+{
+ Job *job = (Job *)opaque;
+ AioContext *aio_context = job->aio_context;
+
+ if (job->driver->exit) {
+ aio_context_acquire(aio_context);
+ job->driver->exit(job);
+ aio_context_release(aio_context);
+ }
+ job_completed(job, job->ret);
+}
/**
* All jobs must allow a pause point before entering their job proper. This
@@ -547,6 +559,12 @@ static void coroutine_fn job_co_entry(void *opaque)
assert(job && job->driver && job->driver->run);
job_pause_point(job);
job->ret = job->driver->run(job, &job->err);
+ if (!job->deferred_to_main_loop) {
+ job->deferred_to_main_loop = true;
+ aio_bh_schedule_oneshot(qemu_get_aio_context(),
+ job_exit,
+ job);
+ }
}
--
2.17.1
- [Qemu-block] [PULL v2 00/10] Block patches, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 01/10] tests: fix bdrv-drain leak, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 02/10] jobs: change start callback to run callback, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 04/10] jobs: add exit shim,
Max Reitz <=
- [Qemu-block] [PULL v2 03/10] jobs: canonize Error object, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 05/10] block/commit: utilize job_exit shim, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 06/10] block/mirror: utilize job_exit shim, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 09/10] jobs: remove ret argument to job_completed; privatize it, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 08/10] block/backup: make function variables consistently named, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 07/10] jobs: utilize job_exit shim, Max Reitz, 2018/08/31
- [Qemu-block] [PULL v2 10/10] jobs: remove job_defer_to_main_loop, Max Reitz, 2018/08/31