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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Will Deacon <will@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Android Kernel Team <kernel-team@android.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Peter Zijlstra <peterz@infradead.org>,
	Segher Boessenkool <segher@kernel.crashing.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Subject: Re: [RFC PATCH 0/8] Rework READ_ONCE() to improve codegen
Date: Fri, 10 Jan 2020 12:14:45 -0800	[thread overview]
Message-ID: <CAHk-=wggv_LmrL85Ez0TLcAku8iz05VZmJxDGo=2aP2VvQtrsA@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a1UzSOHdihbzOn5CZZfo1kvCdj7BAzdQE=PgYS9GBF4Hw@mail.gmail.com>

On Fri, Jan 10, 2020 at 11:47 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> Isn't the read_barrier_depends() the only reason for actually needing
> the temporary local variable that must not be volatile?
>
> If you make alpha provide its own READ_ONCE() as the first
> step, it would seem that the rest of the series gets much easier
> as the others can go back to the simple statement from your

Hmm.. The union still would cause that "take the address of a volatile
thing on the stack" problem, wouldn't it? And that was what caused
most of the issues.

I think the _real_ issue is how KASAN forces that odd pair of inline
functions in order to have the annotations on the accesses.

                Linus

  reply	other threads:[~2020-01-10 20:15 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-10 16:56 [RFC PATCH 0/8] Rework READ_ONCE() to improve codegen Will Deacon
2020-01-10 16:56 ` [RFC PATCH 1/8] compiler/gcc: Emit build-time warning for GCC prior to version 4.8 Will Deacon
2020-01-10 17:35   ` Arnd Bergmann
2020-01-10 17:53     ` Joe Perches
2020-01-13 14:39       ` Arnd Bergmann
2020-01-13 15:35         ` Masahiro Yamada
2020-01-13 14:27     ` Will Deacon
2020-01-14 21:39     ` Nick Desaulniers
2020-01-15 10:35       ` David Laight
2020-01-15 10:49       ` Arnd Bergmann
2020-01-10 16:56 ` [RFC PATCH 2/8] netfilter: Avoid assigning 'const' pointer to non-const pointer Will Deacon
2020-01-10 16:56 ` [RFC PATCH 3/8] fault_inject: Don't rely on "return value" from WRITE_ONCE() Will Deacon
2020-01-10 16:56 ` [RFC PATCH 4/8] READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE() Will Deacon
2020-01-10 16:56 ` [RFC PATCH 5/8] READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses Will Deacon
2020-01-10 19:24   ` Arnd Bergmann
2020-01-13 16:16     ` Will Deacon
2020-01-10 16:56 ` [RFC PATCH 6/8] READ_ONCE: Drop pointer qualifiers when reading from scalar types Will Deacon
2020-01-10 18:54   ` Linus Torvalds
2020-01-13 14:59     ` Will Deacon
2020-01-13 17:42       ` Luc Van Oostenryck
2020-01-13 19:31       ` Linus Torvalds
2020-01-10 16:56 ` [RFC PATCH 7/8] locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros Will Deacon
2020-01-10 19:42   ` Arnd Bergmann
2020-01-13 15:01     ` Will Deacon
2020-01-10 16:56 ` [RFC PATCH 8/8] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros Will Deacon
2020-01-10 17:45   ` Mark Rutland
2020-01-10 17:58 ` [RFC PATCH 0/8] Rework READ_ONCE() to improve codegen Arnd Bergmann
2020-01-10 19:46 ` Arnd Bergmann
2020-01-10 20:14   ` Linus Torvalds [this message]
2020-01-13 13:03     ` Arnd Bergmann
2020-01-13 11:20 ` David Laight
2020-01-13 12:40 ` Christian Borntraeger

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