From: David Howells <dhowells@redhat.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: dhowells@redhat.com, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org, linux-mips@linux-mips.org,
linux-x86_64@vger.kernel.org, linux-s390@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
paulmck@linux.vnet.ibm.com, mingo@kernel.org,
torvalds@linux-foundation.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH/RFC 7/7] kernel: Force ACCESS_ONCE to work only on scalar types
Date: Mon, 24 Nov 2014 13:30:58 +0000 [thread overview]
Message-ID: <15567.1416835858@warthog.procyon.org.uk> (raw)
In-Reply-To: <1416834210-61738-8-git-send-email-borntraeger@de.ibm.com>
Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> +#define get_scalar_volatile_pointer(x) ({ \
> + typeof(x) *__p = &(x); \
> + volatile typeof(x) *__vp = __p; \
> + (void)(long)*__p; __vp; })
> +#define ACCESS_ONCE(x) (*get_scalar_volatile_pointer(x))
Might this cause two loads from memory under some conditions? Once for the
fourth line and once for the fifth?
(Apologies if this has already been discussed)
David
next prev parent reply other threads:[~2014-11-24 13:31 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-24 13:03 [PATCH/RFC 0/7] ACCESS_ONCE and non-scalar accesses Christian Borntraeger
2014-11-24 13:03 ` [PATCH 1/7] KVM: s390: Fix ipte locking Christian Borntraeger
2014-11-24 13:03 ` Christian Borntraeger
2014-11-24 13:03 ` [PATCH/RFC 2/7] mm: replace page table access via ACCESS_ONCE with barriers Christian Borntraeger
2014-11-24 13:03 ` [PATCH/RFC 3/7] x86: Rework ACCESS_ONCE for spinlock code Christian Borntraeger
2014-11-24 13:03 ` Christian Borntraeger
2014-11-24 13:03 ` [PATCH/RFC 4/7] x86: Replace ACCESS_ONCE in gup with a barrier Christian Borntraeger
2014-11-24 13:03 ` [PATCH/RFC 5/7] mips: " Christian Borntraeger
2014-11-24 13:03 ` Christian Borntraeger
2014-11-24 13:03 ` [PATCH/RFC 6/7] arm64: Replace ACCESS_ONCE for spinlock code with barriers Christian Borntraeger
2014-11-24 13:03 ` Christian Borntraeger
2014-11-24 18:50 ` Christian Borntraeger
2014-11-24 13:03 ` [PATCH/RFC 7/7] kernel: Force ACCESS_ONCE to work only on scalar types Christian Borntraeger
2014-11-24 13:30 ` David Howells [this message]
2014-11-24 17:30 ` Linus Torvalds
2014-11-24 18:02 ` Alexei Starovoitov
2014-11-24 18:35 ` Linus Torvalds
2014-11-24 19:07 ` Christian Borntraeger
2014-11-24 19:14 ` Linus Torvalds
2014-11-24 19:42 ` Paul E. McKenney
2014-11-24 20:19 ` Linus Torvalds
2014-11-24 20:46 ` Paul E. McKenney
2014-11-24 20:28 ` Christian Borntraeger
2014-11-24 20:04 ` David Howells
2014-11-24 20:34 ` Linus Torvalds
2014-11-24 20:53 ` Christian Borntraeger
2014-11-24 21:02 ` Linus Torvalds
2014-11-24 21:16 ` Christian Borntraeger
-- strict thread matches above, loose matches on Subject: below --
2014-11-24 20:29 Alexei Starovoitov
2014-11-24 20:45 ` Christian Borntraeger
2014-11-24 20:48 ` Paul E. McKenney
2014-11-24 22:58 Alexei Starovoitov
2014-11-25 0:00 ` Linus Torvalds
2014-11-25 2:28 Alexei Starovoitov
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