From: Oleg Nesterov <oleg@redhat.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: linux-arch@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org,
linux-mm@kvack.org, xen-devel@lists.xenproject.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 4/8] x86/spinlock: Leftover conversion ACCESS_ONCE->READ_ONCE
Date: Thu, 15 Jan 2015 21:01:19 +0100 [thread overview]
Message-ID: <20150115200119.GA29684@redhat.com> (raw)
In-Reply-To: <54B81A37.80109@de.ibm.com>
On 01/15, Christian Borntraeger wrote:
>
> Am 15.01.2015 um 20:38 schrieb Oleg Nesterov:
> > On 01/15, Christian Borntraeger wrote:
> >>
> >> --- a/arch/x86/include/asm/spinlock.h
> >> +++ b/arch/x86/include/asm/spinlock.h
> >> @@ -186,7 +186,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
> >> __ticket_t head = ACCESS_ONCE(lock->tickets.head);
> >>
> >> for (;;) {
> >> - struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets);
> >> + struct __raw_tickets tmp = READ_ONCE(lock->tickets);
> >
> > Agreed, but what about another ACCESS_ONCE() above?
> >
> > Oleg.
>
> tickets.head is a scalar type, so ACCESS_ONCE does work fine with gcc 4.6/4.7.
> My goal was to convert all accesses on non-scalar types
I understand, but READ_ONCE(lock->tickets.head) looks better anyway and
arch_spin_lock() already use READ_ONCE() for this.
So why we should keep the last ACCESS_ONCE() in spinlock.h ? Just to make
another cosmetic cleanup which touches the same function later?
Oleg.
next prev parent reply other threads:[~2015-01-15 20:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-15 8:58 [PATCH 0/8] current ACCESS_ONCE patch queue Christian Borntraeger
2015-01-15 8:58 ` [PATCH 1/8] ppc/kvm: Replace ACCESS_ONCE with READ_ONCE Christian Borntraeger
2015-01-15 23:09 ` Michael Ellerman
2015-01-16 9:43 ` Christian Borntraeger
2015-01-15 8:58 ` [PATCH 2/8] ppc/hugetlbfs: " Christian Borntraeger
2015-01-15 8:58 ` [PATCH 3/8] x86/xen/p2m: " Christian Borntraeger
2015-01-15 9:26 ` Jürgen Groß
2015-01-15 10:43 ` [Xen-devel] " David Vrabel
2015-01-15 11:07 ` Christian Borntraeger
2015-01-15 8:58 ` [PATCH 4/8] x86/spinlock: Leftover conversion ACCESS_ONCE->READ_ONCE Christian Borntraeger
2015-01-15 19:38 ` Oleg Nesterov
2015-01-15 19:51 ` Christian Borntraeger
2015-01-15 20:01 ` Oleg Nesterov [this message]
2015-01-15 21:00 ` Christian Borntraeger
2015-01-15 8:58 ` [PATCH 5/8] mm/gup: Replace ACCESS_ONCE with READ_ONCE Christian Borntraeger
2015-01-15 8:58 ` [PATCH 6/8] kernel: tighten rules for ACCESS ONCE Christian Borntraeger
2015-01-15 8:58 ` [PATCH 7/8] next: sh: Fix compile error Christian Borntraeger
2015-01-15 8:58 ` [PATCH 8/8] kernel: Fix sparse warning for ACCESS_ONCE Christian Borntraeger
2015-01-16 12:12 ` [PATCH 0/8] current ACCESS_ONCE patch queue Alexander Graf
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