From: Jinpu Wang <jinpu.wang@cloud.ionos.com>
To: Roman Penyaev <rpenyaev@suse.de>
Cc: Bart Van Assche <bvanassche@acm.org>,
Jack Wang <jinpuwang@gmail.com>,
linux-block@vger.kernel.org, linux-rdma@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
Sagi Grimberg <sagi@grimberg.me>,
Leon Romanovsky <leon@kernel.org>,
Doug Ledford <dledford@redhat.com>,
Danil Kipnis <danil.kipnis@cloud.ionos.com>
Subject: Re: [PATCH v6 17/25] rnbd: client: main functionality
Date: Fri, 10 Jan 2020 16:29:25 +0100 [thread overview]
Message-ID: <CAMGffE=F1r29pFeKjjrfenPPAj_1s3_m-UbfygReKVXnkqbZSQ@mail.gmail.com> (raw)
In-Reply-To: <2616c4cd0aabcd112256fe2e3d7b9a24@suse.de>
On Fri, Jan 10, 2020 at 4:09 PM Roman Penyaev <rpenyaev@suse.de> wrote:
>
> On 2020-01-10 15:45, Jinpu Wang wrote:
> >> > +{
> >> > + DEFINE_WAIT_FUNC(wait, autoremove_wake_function);
> >> > +
> >> > + prepare_to_wait(&sess->rtrs_waitq, &wait, TASK_UNINTERRUPTIBLE);
> >> > + if (IS_ERR_OR_NULL(sess->rtrs)) {
> >> > + finish_wait(&sess->rtrs_waitq, &wait);
> >> > + return;
> >> > + }
> >> > + mutex_unlock(&sess_lock);
> >> > + /* After unlock session can be freed, so careful */
> >> > + schedule();
> >> > + mutex_lock(&sess_lock);
> >> > +}
> >>
> >> How can a function that calls schedule() and that is not surrounded by
> >> a
> >> loop be correct? What if e.g. schedule() finishes due to a spurious
> >> wakeup?
> > I checked in git history, this no clean explanation why we have to
> > call the mutex_unlock/schedul/mutex_lock magic
> > It's allowed to call schedule inside mutex, seems we can remove the
> > code snip, @Roman Penyaev do you remember why it was introduced?
>
> The loop in question is in the caller, see __find_and_get_sess().
> You can't leave mutex locked and call schedule(), you will catch a
> deadlock with a caller of free_sess(), which has just put the last
> reference and is about to take the sess_lock in order to delete
> the session from the list.
>
> --
> Roman
Thanks Roman for quick reply, will extend the comment
next prev parent reply other threads:[~2020-01-10 15:29 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-30 10:29 [PATCH v6 00/25] RTRS (former IBTRS) rdma transport library and RNBD (former IBNBD) rdma network block device Jack Wang
2019-12-30 10:29 ` [PATCH v6 01/25] sysfs: export sysfs_remove_file_self() Jack Wang
2019-12-30 10:29 ` [PATCH v6 02/25] rtrs: public interface header to establish RDMA connections Jack Wang
2019-12-30 19:25 ` Bart Van Assche
2020-01-02 13:35 ` Jinpu Wang
2020-01-02 16:36 ` Bart Van Assche
2020-01-02 16:47 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 03/25] rtrs: private headers with rtrs protocol structs and helpers Jack Wang
2019-12-30 19:48 ` Bart Van Assche
2020-01-02 15:27 ` Jinpu Wang
2020-01-02 17:00 ` Bart Van Assche
2020-01-02 18:26 ` Jason Gunthorpe
2020-01-03 12:31 ` Jinpu Wang
2020-01-03 12:27 ` Jinpu Wang
2019-12-31 0:07 ` Bart Van Assche
2020-01-03 13:48 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 04/25] rtrs: core: lib functions shared between client and server modules Jack Wang
2019-12-30 22:25 ` Bart Van Assche
2020-01-07 12:22 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 05/25] rtrs: client: private header with client structs and functions Jack Wang
2019-12-30 22:51 ` Bart Van Assche
2020-01-07 12:39 ` Jinpu Wang
2019-12-30 23:03 ` Bart Van Assche
2020-01-07 12:39 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 06/25] rtrs: client: main functionality Jack Wang
2019-12-30 23:53 ` Bart Van Assche
2020-01-02 18:23 ` Jason Gunthorpe
2020-01-03 14:30 ` Jinpu Wang
2020-01-03 16:12 ` Bart Van Assche
2019-12-30 10:29 ` [PATCH v6 07/25] rtrs: client: statistics functions Jack Wang
2020-01-02 21:07 ` Bart Van Assche
2020-01-03 14:39 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 08/25] rtrs: client: sysfs interface functions Jack Wang
2020-01-02 21:14 ` Bart Van Assche
2020-01-03 14:59 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 09/25] rtrs: server: private header with server structs and functions Jack Wang
2020-01-02 21:24 ` Bart Van Assche
2020-01-08 16:33 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 10/25] rtrs: server: main functionality Jack Wang
2020-01-02 22:03 ` Bart Van Assche
2020-01-07 13:19 ` Jinpu Wang
2020-01-07 18:25 ` Jason Gunthorpe
2020-01-10 17:38 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 11/25] rtrs: server: statistics functions Jack Wang
2020-01-02 22:02 ` Bart Van Assche
2020-01-08 12:55 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 12/25] rtrs: server: sysfs interface functions Jack Wang
2020-01-02 22:06 ` Bart Van Assche
2020-01-07 14:40 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 13/25] rtrs: include client and server modules into kernel compilation Jack Wang
2020-01-02 22:11 ` Bart Van Assche
2020-01-03 16:19 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 14/25] rtrs: a bit of documentation Jack Wang
2019-12-30 23:19 ` Bart Van Assche
2020-01-07 14:48 ` Jinpu Wang
2020-01-02 22:21 ` Bart Van Assche
2020-01-07 15:49 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 15/25] rnbd: private headers with rnbd protocol structs and helpers Jack Wang
2020-01-02 22:34 ` Bart Van Assche
2020-01-07 16:53 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 16/25] rnbd: client: private header with client structs and functions Jack Wang
2020-01-02 22:37 ` Bart Van Assche
2020-01-07 17:09 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 17/25] rnbd: client: main functionality Jack Wang
2020-01-02 23:55 ` Bart Van Assche
2020-01-08 14:22 ` Jinpu Wang
2020-01-10 14:45 ` Jinpu Wang
2020-01-10 15:09 ` Roman Penyaev
2020-01-10 15:29 ` Jinpu Wang [this message]
2019-12-30 10:29 ` [PATCH v6 18/25] rnbd: client: sysfs interface functions Jack Wang
2020-01-03 0:03 ` Bart Van Assche
2020-01-08 13:06 ` Jinpu Wang
2020-01-08 16:39 ` Bart Van Assche
2020-01-08 16:51 ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 19/25] rnbd: server: private header with server structs and functions Jack Wang
2019-12-30 10:29 ` [PATCH v6 20/25] rnbd: server: main functionality Jack Wang
2019-12-30 10:29 ` [PATCH v6 21/25] rnbd: server: functionality for IO submission to file or block dev Jack Wang
2019-12-30 10:29 ` [PATCH v6 22/25] rnbd: server: sysfs interface functions Jack Wang
2019-12-30 10:29 ` [PATCH v6 23/25] rnbd: include client and server modules into kernel compilation Jack Wang
2019-12-30 10:29 ` [PATCH v6 24/25] rnbd: a bit of documentation Jack Wang
2019-12-30 10:29 ` [PATCH v6 25/25] MAINTAINERS: Add maintainers for RNBD/RTRS modules Jack Wang
2019-12-30 12:22 ` Gal Pressman
2020-01-02 8:41 ` Jinpu Wang
2019-12-31 0:11 ` [PATCH v6 00/25] RTRS (former IBTRS) rdma transport library and RNBD (former IBNBD) rdma network block device Bart Van Assche
2020-01-02 8:48 ` Jinpu Wang
2019-12-31 2:39 ` Bart Van Assche
2020-01-02 9:20 ` Jinpu Wang
2020-01-02 18:28 ` Jason Gunthorpe
2020-01-03 12:34 ` Jinpu Wang
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