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
Signed-off-by: Fam Zheng
---
blockjob.c | 6 +-
include/block/blockjob.h | 5 +
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/blockjob.c b/blockjob.c
index 80adb9d..b15df93 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -304,7 +304,9 @@ 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);
@@ -478,6 +480,7 @@ 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);
@@ -497,6 +500,7 @@ 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);
}
diff --git a/include/block/blockjob.h b/include/block/blockjob.h
index d84ccd8..8bedc49 100644
--- a/include/block/blockjob.h
+++ b/include/block/blockjob.h
@@ -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;
--
2.4.3