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Date: Wed, 01 Jan 2003 18:11:43 -0800
From: David Brownell <david-b@pacbell.net>
Subject: Re: [PATCH] generic device DMA (dma_pool update)
To: "Adam J. Richter" <adam@yggdrasil.com>
Cc: James Bottomley <James.Bottomley@steeleye.com>, akpm@digeo.com,
       linux-kernel@vger.kernel.org
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James Bottomley wrote:
> adam@yggdrasil.com said:
> 
>>	Can someone show me or invent an example of two different uses of
>>dma_alloc_coherent that really should use different policies on
>>whether to block or not? 
> 
> 
> The obvious one is allocations from interrupt routines, which must be 
> GFP_ATOMIC (ignoring the issue of whether a driver should be doing a memory 
> allocation in an interrupt).  Allocating large pools at driver initialisation 
> should probably be GFP_KERNEL as you say.

More:  not just "from interrupt routines", also "when a spinlock is held".
Though one expects that if a dma_pool were in use, it'd probably have one
of that kind of chunk already available (ideally, even initialized).

Many task-initiated allocations would use GFP_KERNEL; not just major driver
activation points like open().

- Dave

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