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From: Ming Lei <ming.lei@redhat.com>
To: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Khazhy Kumykov <khazhy@google.com>,
	Paolo Valente <paolo.valente@linaro.org>
Subject: Re: [PATCH 2/2] blk: Fix lock inversion between ioc lock and bfqd lock
Date: Fri, 21 May 2021 08:57:08 +0800	[thread overview]
Message-ID: <YKcFZMJiFnsktsBu@T590> (raw)
In-Reply-To: <20210520223353.11561-3-jack@suse.cz>

On Fri, May 21, 2021 at 12:33:53AM +0200, Jan Kara wrote:
> Lockdep complains about lock inversion between ioc->lock and bfqd->lock:
> 
> bfqd -> ioc:
>  put_io_context+0x33/0x90 -> ioc->lock grabbed
>  blk_mq_free_request+0x51/0x140
>  blk_put_request+0xe/0x10
>  blk_attempt_req_merge+0x1d/0x30
>  elv_attempt_insert_merge+0x56/0xa0
>  blk_mq_sched_try_insert_merge+0x4b/0x60
>  bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed

We could move blk_put_request() into scheduler code, then the lock
inversion is avoided. So far only mq-deadline and bfq calls into
blk_mq_sched_try_insert_merge(), and this change should be small.


Thanks,
Ming


  reply	other threads:[~2021-05-21  0:57 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-20 22:33 [PATCH 0/2] block: Fix deadlock when merging requests with BFQ Jan Kara
2021-05-20 22:33 ` [PATCH 1/2] block: Do not merge recursively in elv_attempt_insert_merge() Jan Kara
2021-05-21  0:42   ` Ming Lei
2021-05-21 11:53     ` Jan Kara
2021-05-21 13:12       ` Ming Lei
2021-05-21 13:44         ` Jan Kara
2021-05-20 22:33 ` [PATCH 2/2] blk: Fix lock inversion between ioc lock and bfqd lock Jan Kara
2021-05-21  0:57   ` Ming Lei [this message]
2021-05-21  3:29     ` Khazhy Kumykov
2021-05-21  6:54       ` Ming Lei
2021-05-21 12:05         ` Jan Kara
2021-05-21 13:36           ` Ming Lei
2021-05-21 13:47             ` Jan Kara
2021-05-24 10:04 [PATCH 0/2 v2] block: Fix deadlock when merging requests with BFQ Jan Kara
2021-05-24 10:04 ` [PATCH 2/2] blk: Fix lock inversion between ioc lock and bfqd lock Jan Kara
2021-05-25  0:29   ` Ming Lei
2021-05-28  9:33   ` Paolo Valente
2021-05-28 12:30 [PATCH 0/2 v3] block: Fix deadlock when merging requests with BFQ Jan Kara
2021-05-28 12:30 ` [PATCH 2/2] blk: Fix lock inversion between ioc lock and bfqd lock Jan Kara
2021-06-23  9:36 [PATCH 0/2 v4] block: Fix deadlock when merging requests with BFQ Jan Kara
2021-06-23  9:36 ` [PATCH 2/2] blk: Fix lock inversion between ioc lock and bfqd lock Jan Kara

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