From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>,
corbet@lwn.net, will@kernel.org, mark.rutland@arm.com,
catalin.marinas@arm.com, dennis@kernel.org, tj@kernel.org,
cl@linux.com, hca@linux.ibm.com, gor@linux.ibm.com,
agordeev@linux.ibm.com, borntraeger@linux.ibm.com,
svens@linux.ibm.com, Herbert Xu <herbert@gondor.apana.org.au>,
davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com,
bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org,
hpa@zytor.com, joro@8bytes.org, suravee.suthikulpanit@amd.com,
robin.murphy@arm.com, dwmw2@infradead.org,
baolu.lu@linux.intel.com, Arnd Bergmann <arnd@arndb.de>,
penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com,
Andrew Morton <akpm@linux-foundation.org>,
vbabka@suse.cz, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-s390@vger.kernel.org,
linux-crypto@vger.kernel.org, iommu@lists.linux.dev,
linux-arch@vger.kernel.org
Subject: Re: [RFC][PATCH 05/12] arch: Introduce arch_{,try_}_cmpxchg128{,_local}()
Date: Tue, 20 Dec 2022 16:09:37 +0100 [thread overview]
Message-ID: <Y6HQMVz041V7NruP@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAHk-=wi493ukLwziiqofe=WCSfUU8Qa+LK0mp_GrGWKV3NnTpQ@mail.gmail.com>
On Tue, Dec 20, 2022 at 08:31:19AM -0600, Linus Torvalds wrote:
> On Tue, Dec 20, 2022 at 5:09 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Mon, Dec 19, 2022 at 12:07:25PM -0800, Boqun Feng wrote:
> > >
> > > I wonder whether we should use "(*(u128 *)ptr)" instead of "(*(unsigned
> > > long *) ptr)"? Because compilers may think only 64bit value pointed by
> > > "ptr" gets modified, and they are allowed to do "useful" optimization.
> >
> > In this I've copied the existing cmpxchg_double() code; I'll have to let
> > the arch folks speak here, I've no clue.
>
> It does sound like the right thing to do. I doubt it ends up making a
> difference in practice, but yes, the asm doesn't have a memory
> clobber, so the input/output types should be the right ones for the
> compiler to not possibly do something odd and cache the part that it
> doesn't see as being accessed.
Right, and x86 does just *ptr, without trying to cast away the volatile
even.
I've pushed out a *(u128 *)ptr variant for arm64 and s390, then at least
we'll know if the compiler objects.
next prev parent reply other threads:[~2022-12-20 15:10 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-19 15:35 [RFC][PATCH 00/12] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 01/12] crypto: Remove u128 usage Peter Zijlstra
2022-12-19 15:56 ` Jason A. Donenfeld
2022-12-19 17:00 ` Peter Zijlstra
2022-12-19 17:03 ` Jason A. Donenfeld
2022-12-20 3:50 ` Herbert Xu
2022-12-20 4:11 ` H. Peter Anvin
2022-12-20 4:15 ` Herbert Xu
2022-12-19 15:35 ` [RFC][PATCH 02/12] crypto/ghash-clmulni: Use (struct) be128 Peter Zijlstra
2022-12-20 5:45 ` Eric Biggers
2022-12-19 15:35 ` [RFC][PATCH 03/12] cyrpto/b128ops: Remove struct u128 Peter Zijlstra
2022-12-20 5:52 ` Eric Biggers
2022-12-19 15:35 ` [RFC][PATCH 04/12] types: Introduce [us]128 Peter Zijlstra
2022-12-29 8:30 ` Pavel Machek
2022-12-19 15:35 ` [RFC][PATCH 05/12] arch: Introduce arch_{,try_}_cmpxchg128{,_local}() Peter Zijlstra
2022-12-19 20:07 ` Boqun Feng
2022-12-20 11:08 ` Peter Zijlstra
2022-12-20 14:31 ` Linus Torvalds
2022-12-20 15:09 ` Peter Zijlstra [this message]
2023-01-03 13:25 ` Mark Rutland
2023-01-03 14:03 ` Mark Rutland
2023-01-03 16:19 ` Mark Rutland
2023-01-03 16:50 ` Arnd Bergmann
2023-01-04 11:36 ` Mark Rutland
2023-01-04 13:55 ` Mark Rutland
2022-12-22 1:25 ` Boqun Feng
2022-12-22 13:16 ` Peter Zijlstra
2023-01-03 17:12 ` Heiko Carstens
2023-01-09 18:50 ` Mark Rutland
2023-01-12 10:35 ` Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 06/12] instrumentation: Wire up cmpxchg128() Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 07/12] percpu: Wire up cmpxchg128 Peter Zijlstra
2022-12-29 13:36 ` Arnd Bergmann
2023-01-04 12:09 ` Heiko Carstens
2023-01-09 16:29 ` Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 08/12] s390: Replace cmpxchg_double() with cmpxchg128() Peter Zijlstra
2023-01-10 7:23 ` Heiko Carstens
2023-01-10 8:32 ` Peter Zijlstra
2023-01-10 11:27 ` Mark Rutland
2023-01-10 11:46 ` Heiko Carstens
2023-01-12 11:12 ` Alexander Gordeev
2022-12-19 15:35 ` [RFC][PATCH 09/12] x86,amd_iommu: Replace cmpxchg_double() Peter Zijlstra
2022-12-19 16:47 ` Niklas Schnelle
2022-12-28 8:40 ` Vasant Hegde
2022-12-19 15:35 ` [RFC][PATCH 10/12] x86,intel_iommu: " Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 11/12] slub: " Peter Zijlstra
2023-01-03 15:58 ` Vlastimil Babka
2023-01-03 17:16 ` Heiko Carstens
2023-01-03 19:08 ` Linus Torvalds
2023-01-04 12:07 ` Heiko Carstens
2023-01-09 16:28 ` Peter Zijlstra
2023-01-09 22:02 ` Linus Torvalds
2023-01-09 22:22 ` H. Peter Anvin
2023-01-10 2:09 ` H. Peter Anvin
2023-01-10 10:28 ` Peter Zijlstra
2022-12-19 15:35 ` [RFC][PATCH 12/12] arch: Remove cmpxchg_double Peter Zijlstra
2022-12-22 1:21 ` [RFC][PATCH 00/12] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double() Boqun Feng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Y6HQMVz041V7NruP@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=42.hyeyoo@gmail.com \
--cc=agordeev@linux.ibm.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=baolu.lu@linux.intel.com \
--cc=boqun.feng@gmail.com \
--cc=borntraeger@linux.ibm.com \
--cc=bp@alien8.de \
--cc=catalin.marinas@arm.com \
--cc=cl@linux.com \
--cc=corbet@lwn.net \
--cc=dave.hansen@linux.intel.com \
--cc=davem@davemloft.net \
--cc=dennis@kernel.org \
--cc=dwmw2@infradead.org \
--cc=gor@linux.ibm.com \
--cc=hca@linux.ibm.com \
--cc=herbert@gondor.apana.org.au \
--cc=hpa@zytor.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=iommu@lists.linux.dev \
--cc=joro@8bytes.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-crypto@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-s390@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mingo@redhat.com \
--cc=penberg@kernel.org \
--cc=rientjes@google.com \
--cc=robin.murphy@arm.com \
--cc=roman.gushchin@linux.dev \
--cc=suravee.suthikulpanit@amd.com \
--cc=svens@linux.ibm.com \
--cc=tglx@linutronix.de \
--cc=tj@kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=vbabka@suse.cz \
--cc=will@kernel.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox