Re: [PATCH] blk-mq: run hw queue asynchronously in blk_mq_start_hw_queues

[Jens Axboe]

On 2014-06-24 20:42, Ming Lei wrote:
> On Tue, Jun 24, 2014 at 10:53 PM, Ming Lei <tom.leiming@xxxxxxxxx> wrote:
> >  From API view, it isn't good to run all hw queues synchronously
> > in one context, since it isn't correct for multi hw queue case.
> >
> > So this patch adds 'async' parameter to blk_mq_start_hw_queue(),
> > and make blk_mq_start_hw_queues() to run hw queues asynchronously
> > at default.
>
> BTW, without the change, it is easy to trigger the WARN_ON() in
> __blk_mq_run_hw_queue().

Why not just have it call blk_mq_run_hw_queue()? Pass in async == false, 
but let the cpumask logic sort out if we need to force an async run.

--
Jens Axboe

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0ef2dc7f01bf..ad69ef657e85 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -878,7 +878,7 @@ void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
 	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
 
 	preempt_disable();
-	__blk_mq_run_hw_queue(hctx);
+	blk_mq_run_hw_queue(hctx, false);
 	preempt_enable();
 }
 EXPORT_SYMBOL(blk_mq_start_hw_queue);