Date: Sat, 19 Feb 2005 17:55:13 -0500
From: Jody McIntyre <scjody@modernduck.com>
To: David Brownell <david-b@pacbell.net>
Cc: linux-kernel@vger.kernel.org,
       Linux1394-Devel <linux1394-devel@lists.sourceforge.net>,
       Parag Warudkar <kernel-stuff@comcast.net>
Subject: Re: [PATCH] ohci1394: dma_pool_destroy while in_atomic() && irqs_disabled()
Message-ID: <20050219225513.GI9231@conscoop.ottawa.on.ca>
References: <200502191136.05584.david-b@pacbell.net>
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On Sat, Feb 19, 2005 at 11:36:05AM -0800, David Brownell wrote:
> 
> Those allocations could be from _using_ a dma pool ... but they're
> not from just creating one!
> 
> The cost of creating the dma_pool is the cost of one small kmalloc()
> plus (the expensive part) the /sys/devices/.../pools sysfs attribute
> is created along with the first pool.  (Use that instead of slabinfo
> for those pool allocations.)  That's why the normal spot to create and
> destroy dma pools is in driver probe() and remove() methods.

OK, then I misread drivers/base/pool.c and my objection to the patch is
unfounded.

> If you want to allocate gobs of other stuff at the same time, that's
> your choice ... but it'd be a separate issue.  Cost to create a
> dma_pool is significantly less than PAGE_SIZE, and there's no good
> reason to allocate or destroy those pools anywhere near an IRQ context.

I agree.  raw1394 does far too much with irqs disabled, and moving this
stuff to probe() will fix part of that problem.

Jody

> 
> - Dave
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