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blockjob: Fix hang in block_job_finish_sync

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With a mirror job running on a virtio-blk dataplane disk, sending "q" to
HMP will cause a dead loop in block_job_finish_sync.

This is because the aio_poll() only processes the AIO context of bs
which has no more work to do, while the main loop BH that is scheduled
for setting the job->completed flag is never processed.

Fix this by adding a flag in BlockJob structure, to track which context
to poll for the block job to make progress. Its value is set to true
when block_job_coroutine_complete() is called, and is checked in
block_job_finish_sync to determine which context to poll.

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 1454379144-29807-1-git-send-email-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Fam Zheng 2016-02-02 10:12:24 +08:00 committed by Stefan Hajnoczi
parent ad523bca56
commit 794f01414f
2 changed files with 10 additions and 1 deletions
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6
blockjob.c
View file

@ -296,7 +296,9 @@ static int block_job_finish_sync(BlockJob *job,
return -EBUSY;
}
while (!job->completed) {
aio_poll(bdrv_get_aio_context(bs), true);
aio_poll(job->deferred_to_main_loop ? qemu_get_aio_context() :
bdrv_get_aio_context(bs),
true);
}
ret = (job->cancelled && job->ret == 0) ? -ECANCELED : job->ret;
block_job_unref(job);
@ -470,6 +472,7 @@ static void block_job_defer_to_main_loop_bh(void *opaque)
aio_context = bdrv_get_aio_context(data->job->bs);
aio_context_acquire(aio_context);
data->job->deferred_to_main_loop = false;
data->fn(data->job, data->opaque);
aio_context_release(aio_context);
@ -489,6 +492,7 @@ void block_job_defer_to_main_loop(BlockJob *job,
data->aio_context = bdrv_get_aio_context(job->bs);
data->fn = fn;
data->opaque = opaque;
job->deferred_to_main_loop = true;
qemu_bh_schedule(data->bh);
}

5
include/block/blockjob.h
View file

@ -130,6 +130,11 @@ struct BlockJob {
*/
bool ready;
/**
* Set to true when the job has deferred work to the main loop.
*/
bool deferred_to_main_loop;
/** Status that is published by the query-block-jobs QMP API */
BlockDeviceIoStatus iostatus;