From: Khazhy Kumykov <khazhy@google.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
Paolo Valente <paolo.valente@linaro.org>
Subject: Re: [PATCH 2/2] blk: Fix lock inversion between ioc lock and bfqd lock
Date: Thu, 20 May 2021 20:29:49 -0700 [thread overview]
Message-ID: <CACGdZYKk01Ef7aVjdU9bmL+6Qo99Dc_HqKKiEECGJSsRmADtHQ@mail.gmail.com> (raw)
In-Reply-To: <YKcFZMJiFnsktsBu@T590>
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On Thu, May 20, 2021 at 5:57 PM Ming Lei <ming.lei@redhat.com> wrote:
>
> 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.
We'd potentially be putting multiple requests if we keep the recursive merge.
Could we move backmerge loop to the schedulers, perhaps?
>
>
> Thanks,
> Ming
>
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next prev parent reply other threads:[~2021-05-21 3:30 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
2021-05-21 3:29 ` Khazhy Kumykov [this message]
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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