From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35282) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aOyfN-0007H5-Om for qemu-devel@nongnu.org; Thu, 28 Jan 2016 21:20:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aOyfM-0001g1-LF for qemu-devel@nongnu.org; Thu, 28 Jan 2016 21:20:05 -0500 From: Fam Zheng Date: Fri, 29 Jan 2016 10:19:49 +0800 Message-Id: <1454033989-16996-1-git-send-email-famz@redhat.com> Subject: [Qemu-devel] [PATCH v3] blockjob: Fix hang in block_job_finish_sync List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , qemu-block@nongnu.org, Jeff Cody , mreitz@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, jsnow@redhat.com 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 | 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