From: Linus Torvalds <torvalds@linux-foundation.org>
To: Roman Pen <roman.penyaev@profitbricks.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>,
linux-block <linux-block@vger.kernel.org>,
linux-rdma <linux-rdma@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
Sagi Grimberg <sagi@grimberg.me>,
Bart Van Assche <bart.vanassche@sandisk.com>,
Or Gerlitz <ogerlitz@mellanox.com>,
Doug Ledford <dledford@redhat.com>,
swapnil.ingle@profitbricks.com, danil.kipnis@profitbricks.com,
Jinpu Wang <jinpu.wang@profitbricks.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 01/26] rculist: introduce list_next_or_null_rr_rcu()
Date: Mon, 21 May 2018 08:16:59 -0700 [thread overview]
Message-ID: <CA+55aFymFCVqh4VxtqDPoFYh6zsGEDLSV79_AnsMp3M=t2mhqg@mail.gmail.com> (raw)
In-Reply-To: <CAJrWOzBenkHg_5zs1VAxP_rVbCbOJO_eO0toJBhnzXuy_yWH2Q@mail.gmail.com>
On Mon, May 21, 2018 at 6:51 AM Roman Penyaev <
roman.penyaev@profitbricks.com> wrote:
> No, I continue from the pointer, which I assigned on the previous IO
> in order to send IO fairly and keep load balanced.
Right. And that's exactly what has both me and Paul nervous. You're no
longer in the RCU domain. You're using a pointer where the lifetime has
nothing to do with RCU any more.
Can it be done? Sure. But you need *other* locking for it (that you haven't
explained), and it's fragile as hell.
It's probably best to not use RCU for it at all, but depend on that "other
locking" that you have to have anyway, to keep the pointer valid over the
non-RCU region.
Linus
next prev parent reply other threads:[~2018-05-21 15:16 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-18 13:03 [PATCH v2 00/26] InfiniBand Transport (IBTRS) and Network Block Device (IBNBD) Roman Pen
2018-05-18 13:03 ` [PATCH v2 01/26] rculist: introduce list_next_or_null_rr_rcu() Roman Pen
2018-05-18 16:56 ` Linus Torvalds
2018-05-19 20:25 ` Roman Penyaev
2018-05-19 21:04 ` Linus Torvalds
2018-05-19 16:37 ` Paul E. McKenney
2018-05-19 20:20 ` Roman Penyaev
2018-05-19 20:56 ` Linus Torvalds
2018-05-20 0:43 ` Paul E. McKenney
2018-05-21 13:50 ` Roman Penyaev
2018-05-21 15:16 ` Linus Torvalds [this message]
2018-05-21 15:33 ` Paul E. McKenney
2018-05-22 9:09 ` Roman Penyaev
2018-05-22 16:36 ` Paul E. McKenney
2018-05-22 16:38 ` Linus Torvalds
2018-05-22 17:04 ` Paul E. McKenney
2018-05-21 15:31 ` Paul E. McKenney
2018-05-22 9:09 ` Roman Penyaev
2018-05-22 17:03 ` Paul E. McKenney
2018-05-18 13:03 ` [PATCH v2 02/26] sysfs: export sysfs_remove_file_self() Roman Pen
2018-05-18 15:08 ` Tejun Heo
2018-05-18 13:03 ` [PATCH v2 03/26] ibtrs: public interface header to establish RDMA connections Roman Pen
2018-05-18 13:03 ` [PATCH v2 04/26] ibtrs: private headers with IBTRS protocol structs and helpers Roman Pen
2018-05-18 13:03 ` [PATCH v2 05/26] ibtrs: core: lib functions shared between client and server modules Roman Pen
2018-05-18 13:03 ` [PATCH v2 06/26] ibtrs: client: private header with client structs and functions Roman Pen
2018-05-18 13:03 ` [PATCH v2 07/26] ibtrs: client: main functionality Roman Pen
2018-05-18 13:03 ` [PATCH v2 08/26] ibtrs: client: statistics functions Roman Pen
2018-05-18 13:03 ` [PATCH v2 09/26] ibtrs: client: sysfs interface functions Roman Pen
2018-05-18 13:03 ` [PATCH v2 10/26] ibtrs: server: private header with server structs and functions Roman Pen
2018-05-18 13:03 ` [PATCH v2 11/26] ibtrs: server: main functionality Roman Pen
2018-05-18 13:03 ` [PATCH v2 12/26] ibtrs: server: statistics functions Roman Pen
2018-05-18 13:04 ` [PATCH v2 13/26] ibtrs: server: sysfs interface functions Roman Pen
2018-05-18 13:04 ` [PATCH v2 14/26] ibtrs: include client and server modules into kernel compilation Roman Pen
2018-05-20 22:14 ` kbuild test robot
2018-05-21 6:36 ` kbuild test robot
2018-05-22 5:05 ` Leon Romanovsky
2018-05-22 9:27 ` Roman Penyaev
2018-05-22 13:18 ` Leon Romanovsky
2018-05-22 16:12 ` Roman Penyaev
2018-05-18 13:04 ` [PATCH v2 15/26] ibtrs: a bit of documentation Roman Pen
2018-05-18 13:04 ` [PATCH v2 16/26] ibnbd: private headers with IBNBD protocol structs and helpers Roman Pen
2018-05-18 13:04 ` [PATCH v2 17/26] ibnbd: client: private header with client structs and functions Roman Pen
2018-05-18 13:04 ` [PATCH v2 18/26] ibnbd: client: main functionality Roman Pen
2018-05-18 13:04 ` [PATCH v2 19/26] ibnbd: client: sysfs interface functions Roman Pen
2018-05-18 13:04 ` [PATCH v2 20/26] ibnbd: server: private header with server structs and functions Roman Pen
2018-05-18 13:04 ` [PATCH v2 21/26] ibnbd: server: main functionality Roman Pen
2018-05-18 13:04 ` [PATCH v2 22/26] ibnbd: server: functionality for IO submission to file or block dev Roman Pen
2018-05-18 13:04 ` [PATCH v2 23/26] ibnbd: server: sysfs interface functions Roman Pen
2018-05-18 13:04 ` [PATCH v2 24/26] ibnbd: include client and server modules into kernel compilation Roman Pen
2018-05-20 17:21 ` kbuild test robot
2018-05-20 22:14 ` kbuild test robot
2018-05-21 5:33 ` kbuild test robot
2018-05-18 13:04 ` [PATCH v2 25/26] ibnbd: a bit of documentation Roman Pen
2018-05-18 13:04 ` [PATCH v2 26/26] MAINTAINERS: Add maintainer for IBNBD/IBTRS modules Roman Pen
2018-05-22 16:45 ` [PATCH v2 00/26] InfiniBand Transport (IBTRS) and Network Block Device (IBNBD) Jason Gunthorpe
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