From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: Driver supported smp linux kernel need use smp_wmb/smp_rmb, nor wmb/rmb?
Date: Thu, 26 Aug 2010 10:18:04 +0100 [thread overview]
Message-ID: <20100826091804.GA8212@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <AANLkTimOaRrEGCYH6k_3wfDixnk1RkJ5JCSi_hv8PQsC@mail.gmail.com>
On Thu, Aug 26, 2010 at 03:43:29PM +0800, David Yang wrote:
> Start with linux 2.6.33, the DMA coherent buffers are mapped as Normal
> Non-cacheable, so our drivers using dma_alloc_coherent() add the
> barriers (e.g. wmb/rmb) to ensure that read/wirte coherence with
> devices.
>
> Now our drivers are stable at the non-smp linux 2.6.33, if our driver
> need support the smp linux 2.6.33, we need replace wmb()/rmb() to
> smp_wmb()/smp_rmb()?
No. smp_* barriers are compiler barriers on uniprocessor, and mandatory
barriers on SMP systems.
If you definitely need a barrier for UP, then use the non-smp_ versions.
prev parent reply other threads:[~2010-08-26 9:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-26 7:43 Driver supported smp linux kernel need use smp_wmb/smp_rmb, nor wmb/rmb? David Yang
2010-08-26 9:18 ` Russell King - ARM Linux [this message]
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