From: okaya@codeaurora.org
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Alexander Duyck <alexander.duyck@gmail.com>,
Will Deacon <will.deacon@arm.com>, Arnd Bergmann <arnd@arndb.de>,
Jason Gunthorpe <jgg@ziepe.ca>,
David Laight <David.Laight@aculab.com>, Oliver <oohall@gmail.com>,
"open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)"
<linuxppc-dev@lists.ozlabs.org>,
linux-rdma@vger.kernel.org,
Alexander Duyck <alexander.h.duyck@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
netdev@vger.kernel.org, linus971@gmail.com
Subject: Re: RFC on writel and writel_relaxed
Date: Wed, 28 Mar 2018 07:41:16 -0400 [thread overview]
Message-ID: <b02cc752d90c5e5ae2cc8cc4f67429a7@codeaurora.org> (raw)
In-Reply-To: <CA+55aFxULkhZGhg-tTBBxBBvXbL7QV7f6zvwW7U2wHFijqGEqw@mail.gmail.com>
On 2018-03-28 02:14, Linus Torvalds wrote:
> On Tue, Mar 27, 2018 at 5:24 PM, Sinan Kaya <okaya@codeaurora.org>
> wrote:
>>
>> Basically changing it to
>>
>> dma_buffer->foo = 1; /* WB */
>> wmb()
>> writel_relaxed(KICK, DMA_KICK_REGISTER); /* UC */
>> mmiowb()
>
> Why?
>
> Why not just remove the wmb(), and keep the barrier in the writel()?
Yes, we want to get there indeed. It is because of some arch not
implementing writel properly. Maintainers want to play safe.
That is why I asked if IA64 and other well known archs follow the
strongly ordered rule at this moment like PPC and ARM.
Or should we go and inform every arch about this before yanking wmb()?
Maintainers are afraid of introducing a regression.
>
> The above code makes no sense, and just looks stupid to me. It also
> generates pointlessly bad code on x86, so it's bad there too.
>
> Linus
next prev parent reply other threads:[~2018-03-28 11:41 UTC|newest]
Thread overview: 129+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-21 3:07 RFC on writel and writel_relaxed Sinan Kaya
2018-03-21 3:40 ` Oliver
2018-03-21 13:53 ` Sinan Kaya
2018-03-21 13:58 ` Sinan Kaya
2018-03-26 13:43 ` Arnd Bergmann
2018-03-26 16:00 ` Sinan Kaya
2018-03-21 14:35 ` David Laight
2018-03-21 15:04 ` Sinan Kaya
2018-03-22 5:24 ` Oliver
2018-03-22 8:20 ` Gabriel Paubert
2018-03-22 9:25 ` Oliver
2018-03-22 11:25 ` Gabriel Paubert
2018-03-22 10:37 ` David Laight
2018-03-22 4:24 ` Benjamin Herrenschmidt
2018-03-22 10:15 ` Oliver
2018-03-22 13:52 ` Benjamin Herrenschmidt
2018-03-22 17:51 ` Sinan Kaya
2018-03-23 0:16 ` Benjamin Herrenschmidt
2018-03-23 13:42 ` Sinan Kaya
2018-03-24 1:22 ` Benjamin Herrenschmidt
2018-03-24 15:06 ` Sinan Kaya
2018-03-26 11:44 ` Will Deacon
2018-03-26 12:11 ` okaya
2018-03-26 12:42 ` Sinan Kaya
2018-03-23 16:35 ` Jason Gunthorpe
2018-03-24 1:23 ` Benjamin Herrenschmidt
2018-03-26 11:08 ` David Laight
2018-03-26 16:54 ` Jason Gunthorpe
2018-03-26 19:44 ` Arnd Bergmann
2018-03-26 20:25 ` Jason Gunthorpe
2018-03-26 20:43 ` Arnd Bergmann
2018-03-26 21:09 ` Jason Gunthorpe
2018-03-26 21:30 ` Arnd Bergmann
2018-03-26 21:46 ` Sinan Kaya
2018-03-26 22:01 ` Benjamin Herrenschmidt
2018-03-26 22:08 ` Sinan Kaya
2018-03-26 22:28 ` Benjamin Herrenschmidt
2018-03-26 22:27 ` Jason Gunthorpe
2018-03-26 22:36 ` Benjamin Herrenschmidt
2018-03-26 22:42 ` Benjamin Herrenschmidt
2018-03-26 22:50 ` Jason Gunthorpe
2018-03-26 23:59 ` Benjamin Herrenschmidt
2018-03-27 1:39 ` Jason Gunthorpe
2018-03-27 7:56 ` Arnd Bergmann
2018-03-27 8:56 ` Benjamin Herrenschmidt
2018-03-27 9:44 ` Arnd Bergmann
2018-03-27 10:00 ` Will Deacon
2018-03-27 11:23 ` Benjamin Herrenschmidt
2018-03-27 12:22 ` okaya
2018-03-27 14:12 ` Jason Gunthorpe
2018-03-27 21:27 ` Benjamin Herrenschmidt
2018-03-27 9:57 ` Will Deacon
2018-03-27 10:05 ` Arnd Bergmann
2018-03-27 10:09 ` Will Deacon
2018-03-27 10:53 ` Arnd Bergmann
2018-03-27 11:02 ` Will Deacon
2018-03-27 11:05 ` Arnd Bergmann
2018-03-27 11:25 ` Benjamin Herrenschmidt
2018-03-27 13:20 ` David Laight
2018-03-27 13:46 ` Sinan Kaya
2018-03-27 14:36 ` Will Deacon
2018-03-27 21:29 ` Benjamin Herrenschmidt
2018-03-28 8:53 ` Will Deacon
2018-03-28 9:00 ` David Laight
2018-03-28 9:09 ` Will Deacon
2018-03-28 9:56 ` Benjamin Herrenschmidt
2018-03-28 9:50 ` Benjamin Herrenschmidt
2018-03-28 9:55 ` Arnd Bergmann
2018-03-28 10:01 ` Benjamin Herrenschmidt
2018-03-28 10:13 ` Will Deacon
2018-03-28 16:57 ` Jason Gunthorpe
2018-03-29 9:19 ` Will Deacon
2018-03-29 14:45 ` Jason Gunthorpe
2018-03-29 14:58 ` David Laight
2018-03-29 16:40 ` Jason Gunthorpe
2018-03-27 21:24 ` Benjamin Herrenschmidt
2018-03-27 11:21 ` Benjamin Herrenschmidt
2018-03-27 9:42 ` Will Deacon
2018-03-27 11:20 ` Benjamin Herrenschmidt
2018-03-27 11:24 ` Will Deacon
2018-03-27 14:24 ` Jason Gunthorpe
2018-03-27 14:16 ` Jason Gunthorpe
2018-03-26 22:00 ` Benjamin Herrenschmidt
2018-03-27 14:46 ` Sinan Kaya
2018-03-27 15:01 ` Jose Abreu
2018-03-27 15:10 ` Will Deacon
2018-03-27 18:54 ` Alexander Duyck
2018-03-27 19:54 ` Arnd Bergmann
2018-03-27 20:46 ` Arnd Bergmann
2018-03-27 21:33 ` Benjamin Herrenschmidt
2018-03-28 0:39 ` Linus Torvalds
2018-03-28 1:03 ` Benjamin Herrenschmidt
2018-03-28 2:51 ` Linus Torvalds
2018-03-28 3:24 ` Sinan Kaya
2018-03-28 4:41 ` Benjamin Herrenschmidt
2018-03-28 6:14 ` Linus Torvalds
2018-03-28 11:41 ` okaya [this message]
2018-03-28 15:13 ` Benjamin Herrenschmidt
2018-03-28 15:55 ` David Miller
2018-03-28 16:23 ` Nicholas Piggin
2018-03-28 21:31 ` Benjamin Herrenschmidt
2018-03-28 22:09 ` Nicholas Piggin
2018-03-29 9:20 ` Will Deacon
2018-03-29 13:56 ` Sinan Kaya
2018-03-29 14:04 ` David Miller
2018-03-29 16:29 ` Arnd Bergmann
2018-03-29 16:59 ` Sinan Kaya
2018-03-30 1:40 ` Benjamin Herrenschmidt
2018-04-02 13:01 ` Sinan Kaya
2018-03-28 4:33 ` Benjamin Herrenschmidt
2018-03-28 6:26 ` Linus Torvalds
2018-03-28 6:42 ` Benjamin Herrenschmidt
2018-03-28 6:53 ` Linus Torvalds
2018-03-28 6:56 ` Benjamin Herrenschmidt
2018-03-28 7:11 ` Arnd Bergmann
2018-03-28 7:42 ` Benjamin Herrenschmidt
2018-03-28 9:07 ` Will Deacon
2018-03-28 9:56 ` Benjamin Herrenschmidt
2018-03-28 10:13 ` Aw: " Lino Sanfilippo
2018-03-28 10:20 ` Benjamin Herrenschmidt
2018-03-28 11:30 ` David Laight
2018-03-28 15:12 ` Benjamin Herrenschmidt
2018-03-28 16:16 ` David Laight
2018-03-28 1:21 ` Benjamin Herrenschmidt
2018-03-27 21:35 ` Benjamin Herrenschmidt
2018-03-26 21:26 ` Benjamin Herrenschmidt
-- strict thread matches above, loose matches on Subject: below --
2018-03-27 21:54 Alexander Duyck
2018-03-27 22:35 ` Sinan Kaya
2018-03-27 23:43 ` Benjamin Herrenschmidt
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