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[Qemu-block] [PATCH v3] blockjob: Fix hang in block_job_finish_sync
From: |
Fam Zheng |
Subject: |
[Qemu-block] [PATCH v3] blockjob: Fix hang in block_job_finish_sync |
Date: |
Fri, 29 Jan 2016 10:19:49 +0800 |
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 <address@hidden>
Signed-off-by: Fam Zheng <address@hidden>
---
blockjob.c | 5 ++++-
include/block/blockjob.h | 9 +++++++++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/blockjob.c b/blockjob.c
index 80adb9d..25e1581 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);
@@ -497,6 +499,7 @@ 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..550de26 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;
@@ -402,6 +407,10 @@ typedef void BlockJobDeferToMainLoopFn(BlockJob *job, void
*opaque);
* AioContext acquired. Block jobs must call bdrv_unref(), bdrv_close(), and
* anything that uses bdrv_drain_all() in the main loop.
*
+ * The job->deferred_to_main_loop flag will be set. Caller must clear it once
+ * the deferred work is done and the block job coroutine continues, unless it's
+ * completing immediately.
+ *
* The @job AioContext is held while @fn executes.
*/
void block_job_defer_to_main_loop(BlockJob *job,
--
2.4.3
- [Qemu-block] [PATCH v3] blockjob: Fix hang in block_job_finish_sync,
Fam Zheng <=