linux-kernel - Re: [RFC PATCH] blk-mq: fixup RESTART when queue becomes idle

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Date:   Fri, 19 Jan 2018 15:20:13 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "ming.lei@...hat.com" <ming.lei@...hat.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "dm-devel@...hat.com" <dm-devel@...hat.com>,
        "hch@...radead.org" <hch@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "osandov@...com" <osandov@...com>,
        "snitzer@...hat.com" <snitzer@...hat.com>
Subject: Re: [RFC PATCH] blk-mq: fixup RESTART when queue becomes idle

On Fri, 2018-01-19 at 15:26 +0800, Ming Lei wrote:
> Please see queue_delayed_work_on(), hctx->run_work is shared by all
> scheduling, once blk_mq_delay_run_hw_queue(100ms) returns, no new
> scheduling can make progress during the 100ms.

How about addressing that as follows:

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f7515dd95a36..57f8379a476d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1403,9 +1403,9 @@ static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
 		put_cpu();
 	}
 
-	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
-					 &hctx->run_work,
-					 msecs_to_jiffies(msecs));
+	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
+				    &hctx->run_work,
+				    msecs_to_jiffies(msecs));
 }
 
 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)

Bart.