From: Boqun Feng <boqun.feng@gmail.com>
To: Olivier Dion <odion@efficios.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
rnk@google.com, Alan Stern <stern@rowland.harvard.edu>,
Andrea Parri <parri.andrea@gmail.com>,
Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Nicholas Piggin <npiggin@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
"Paul E. McKenney" <paulmck@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Tom Rix <trix@redhat.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
gcc@gcc.gnu.org, llvm@lists.linux.dev
Subject: Re: [RFC] Bridging the gap between the Linux Kernel Memory Consistency Model (LKMM) and C11/C++11 atomics
Date: Wed, 5 Jul 2023 00:05:32 -0700 [thread overview]
Message-ID: <ZKUWPKWAnjZvqsgL@Boquns-Mac-mini.local> (raw)
In-Reply-To: <87ttukdcow.fsf@laura>
On Mon, Jul 03, 2023 at 03:20:31PM -0400, Olivier Dion wrote:
[...]
> NOTE: On x86-64, we found at least one corner case [7] with Clang where
> a RELEASE exchange is optimized to a RELEASE store, when the returned
> value of the exchange is unused, breaking the above expectations.
> Although this type of optimization respect the standard "as-if"
> statement, we question its pertinence since a user should simply do a
> RELEASE store instead of an exchange in that case. With the
> introduction of these new primitives, these type of optimizations should
> be revisited.
>
FWIW, this is actually a LLVM bug:
https://github.com/llvm/llvm-project/issues/60418
Regards,
Boqun
next prev parent reply other threads:[~2023-07-05 7:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-03 19:20 [RFC] Bridging the gap between the Linux Kernel Memory Consistency Model (LKMM) and C11/C++11 atomics Olivier Dion
2023-07-03 20:27 ` Alan Stern
2023-07-04 17:19 ` Olivier Dion
2023-07-04 20:25 ` Alan Stern
2023-07-04 21:25 ` Paul E. McKenney
2023-07-06 16:37 ` Olivier Dion
2023-07-04 9:46 ` Peter Zijlstra
2023-07-04 10:23 ` Jonathan Wakely
2023-07-07 15:31 ` Mathieu Desnoyers
2023-07-07 14:04 ` Olivier Dion
2023-07-07 15:45 ` Peter Zijlstra
2023-07-05 7:05 ` Boqun Feng [this message]
2023-07-05 13:16 ` Mathieu Desnoyers
2023-07-07 10:40 ` Jonas Oberhauser
2023-07-07 17:25 ` Olivier Dion
2023-07-10 14:32 ` Jonas Oberhauser
2023-08-16 14:31 ` Mathieu Desnoyers
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