Re: [PATCH] 1/3 Implement generic device DMA mapping support

[Takashi Iwai <tiwai@suse.de>]

At Mon, 01 Mar 2004 19:34:57 +0100,
I wrote:
> 
> At Mon, 1 Mar 2004 18:22:24 +0000,
> Russell King wrote:
> > 
> > On Mon, Mar 01, 2004 at 06:51:56PM +0100, Takashi Iwai wrote:
> > > a small concern about GFP_KERNEL is that i experienced the stall when
> > > the kernel tried to allocate large continuous pages with GFP_KERNEL,
> > > e.g. modprobe stops infinitely in the module init phase (and you
> > > cannot even interrupt that process).
> > > 
> > > does dma_alloc_coherent(GFP_KERNEL) with big pages work without stall?
> > 
> > It depends where the stall was coming from.  Do you have any further
> > details?
> 
> first of alll, i have to mention that it happend in the time of 2.4
> kernels.  i've not tested with 2.6 kernels at all.
> 
> a typical case was es1968 driver, which allocates the all buffer pages
> at the initialization.  when __get_free_pages() for 256MB with
> GFP_KERNEL is called, it goes to sleep and never gets back.  since
> the context is uninterruptible, modprobe stucks and doesn't accept
> SIGKILL.
> 
> anyway, i need to this behavior again with the recent kernel.

ok, i tested the new code now.
it seems working fine without stall even for es1968 driver.

the only problem is the call traces for each allocation like:

	modprobe: page allocation failure. order:8, mode:0xd0
	Call Trace:
	 [<c013939c>] __alloc_pages+0x2ec/0x300
	 [<c0139418>] __get_free_pages+0x18/0x30
	...

i know it's just a warning but surely it's annoying if the caller
knows the allocation may fail.  it would be nice if we can shut it
up.


Takashi


-------------------------------------------------------
SF.Net is sponsored by: Speed Start Your Linux Apps Now.
Build and deploy apps & Web services for Linux with
a free DVD software kit from IBM. Click Now!
http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click