From: Waiman Long <waiman.long@hp.com>
To: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org, peterz@infradead.org,
linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com
Subject: Re: [PATCH v2 7/7] ARM: atomics: define our SMP atomics in terms of _relaxed operations
Date: Thu, 16 Jul 2015 16:40:03 -0400 [thread overview]
Message-ID: <55A816A3.1000502@hp.com> (raw)
In-Reply-To: <1437060758-10381-8-git-send-email-will.deacon@arm.com>
On 07/16/2015 11:32 AM, Will Deacon wrote:
> By defining our SMP atomics in terms of relaxed operations, we gain
> a small reduction in code size and have acquire/release/fence variants
> generated automatically by the core code.
>
> Signed-off-by: Will Deacon<will.deacon@arm.com>
> ---
> arch/arm/include/asm/atomic.h | 37 ++++++++++++++-------------------
> arch/arm/include/asm/cmpxchg.h | 47 +++++++-----------------------------------
> 2 files changed, 24 insertions(+), 60 deletions(-)
>
>
>
> -#define xchg(ptr, x) ({ \
> +#define xchg_relaxed(ptr, x) ({ \
> (__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr), \
> sizeof(*(ptr))); \
> })
> @@ -117,6 +115,8 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size
> #error "SMP is not supported on this platform"
> #endif
>
> +#define xchg xchg_relaxed
Is that a typo? I think xchg() needs to be a full memory barrier.
Cheers,
Longman
next prev parent reply other threads:[~2015-07-16 20:40 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 15:32 [PATCH v2 0/7] Add generic support for relaxed atomics Will Deacon
2015-07-16 15:32 ` [PATCH v2 1/7] atomics: add acquire/release/relaxed variants of some atomic operations Will Deacon
2015-07-17 0:07 ` Waiman Long
2015-07-17 9:40 ` Will Deacon
2015-07-17 17:19 ` Waiman Long
2015-07-17 17:30 ` Will Deacon
2015-07-16 15:32 ` [PATCH v2 2/7] asm-generic: rework atomic-long.h to avoid bulk code duplication Will Deacon
2015-07-16 15:32 ` [PATCH v2 3/7] asm-generic: add relaxed/acquire/release variants for atomic_long_t Will Deacon
2015-07-16 15:32 ` [PATCH v2 4/7] lockref: remove homebrew cmpxchg64_relaxed macro definition Will Deacon
2015-07-16 16:48 ` Peter Zijlstra
2015-07-16 17:00 ` Will Deacon
2015-07-16 15:32 ` [PATCH v2 5/7] locking/qrwlock: make use of acquire/release/relaxed atomics Will Deacon
2015-07-16 16:59 ` Peter Zijlstra
2015-07-16 18:13 ` Will Deacon
2015-07-16 15:32 ` [PATCH v2 6/7] include/llist: use linux/atomic.h instead of asm/cmpxchg.h Will Deacon
2015-07-16 15:32 ` [PATCH v2 7/7] ARM: atomics: define our SMP atomics in terms of _relaxed operations Will Deacon
2015-07-16 20:40 ` Waiman Long [this message]
2015-07-16 21:08 ` Peter Zijlstra
2015-07-17 0:00 ` Waiman Long
2015-07-17 9:35 ` Will Deacon
2015-07-17 17:17 ` Waiman Long
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