* Driver supported smp linux kernel need use smp_wmb/smp_rmb, nor wmb/rmb?
@ 2010-08-26 7:43 David Yang
2010-08-26 9:18 ` Russell King - ARM Linux
0 siblings, 1 reply; 2+ messages in thread
From: David Yang @ 2010-08-26 7:43 UTC (permalink / raw)
To: linux-arm-kernel
Hello all,
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()?
Thank for any help
David
^ permalink raw reply [flat|nested] 2+ messages in thread
* Driver supported smp linux kernel need use smp_wmb/smp_rmb, nor wmb/rmb?
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
0 siblings, 0 replies; 2+ messages in thread
From: Russell King - ARM Linux @ 2010-08-26 9:18 UTC (permalink / raw)
To: linux-arm-kernel
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.
^ permalink raw reply [flat|nested] 2+ messages in thread
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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
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