From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.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 08:31:19 -0600 [thread overview]
Message-ID: <CAHk-=wi493ukLwziiqofe=WCSfUU8Qa+LK0mp_GrGWKV3NnTpQ@mail.gmail.com> (raw)
In-Reply-To: <Y6GXoO4qmH9OIZ5Q@hirez.programming.kicks-ass.net>
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.
Linus
next prev parent reply other threads:[~2022-12-20 14:32 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 [this message]
2022-12-20 15:09 ` Peter Zijlstra
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
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