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Re: [Qemu-devel] [PATCH 02/20] blockjob: introduce .drain callback for j
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [Qemu-devel] [PATCH 02/20] blockjob: introduce .drain callback for jobs |
Date: |
Fri, 2 Dec 2016 17:01:30 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 |
27.10.2016 13:48, Paolo Bonzini wrote:
This is required to decouple block jobs from running in an
AioContext. With multiqueue block devices, a BlockDriverState
does not really belong to a single AioContext.
The solution is to first wait until all I/O operations are
complete; then loop in the main thread for the block job to
complete entirely.
Signed-off-by: Paolo Bonzini <address@hidden>
---
[...]
@@ -413,14 +409,21 @@ static int block_job_finish_sync(BlockJob *job,
assert(blk_bs(job->blk)->job == job);
block_job_ref(job);
+
finish(job, &local_err);
if (local_err) {
error_propagate(errp, local_err);
block_job_unref(job);
return -EBUSY;
}
+ /* block_job_drain calls block_job_enter, and it should be enough to
+ * induce progress until the job completes or moves to the main thread.
+ */
Hi Paolo!
Looks like I have a problem with this. block_job_drain enters the job
only if job.busy = false. But what if job yielded with busy = true?
My case is the following: in the job I call co_aio_sleep_ns() for some
time without setting job.busy to false, and it looks like timer doesn't
work while we are in "while() { block_job_drain() }" loop. If I just set
"job.busy = false" and "job.busy = true" around co_aio_sleep_ns() all
start to work.
I don't want set job.busy to false, because actually job is working -
several additional coroutines do their work, only the main one (job.co)
do nothing. I can remove timer, and make other coroutines wake up the
main one when it needed, and, anyway it looks like better way..
But the question is: is it ok, that we can't use sleep timer in the job,
without setting busy = true? Is it right that only io can wake up block
job coroutine, if it yielded without setting busy=false?
+ while (!job->deferred_to_main_loop && !job->completed) {
+ block_job_drain(job);
+ }
while (!job->completed) {
- aio_poll(block_job_get_aio_context(job), true);
+ aio_poll(qemu_get_aio_context(), true);
}
ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
block_job_unref(job);
--
Best regards,
Vladimir
- Re: [Qemu-devel] [PATCH 02/20] blockjob: introduce .drain callback for jobs,
Vladimir Sementsov-Ogievskiy <=