linux-kernel - Re: [PATCH -v3 1/4] pci, usb: Make usb handoff func all take base remapping

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Date:	Mon, 10 Jan 2011 22:34:27 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Greg KH <greg@...ah.com>, Jesse Barnes <jbarnes@...tuousgeek.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	linux-usb@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v3 1/4] pci, usb:  Make usb handoff func all take base
 remapping

On 01/10/2011 09:21 PM, Benjamin Herrenschmidt wrote:
> On Mon, 2011-01-10 at 17:20 -0800, Yinghai Lu wrote:
>>
>> for early access, can not use udelay yet, it will take some one.
>> Also msleep will cause crash, because it needs scheduler there.
> 
> Right, and that's for such special cases (hopefully rare) that we have
> system_state... Much better than your function pointers I reckon.

system_state does not work.
it only have BOOTING and RUNNING ...
RUNNING is set in init/main.c::init_post().
so early_quirk and pci_quirk all with BOOTING stage...

 slab_is_available() could be used, but looks alike abuse.

> 
> We could even wrap it into a safe_delay() function or whatever (in fact
> why not make msleep() itself safe ? It's not like it was timing critical
> code :-)

like 
void safe_udelay(unsigned long usecs)
{
	if (slab_is_available())
		udelay(usecs)
	else
		early_udelay(usecs);
}

or wonder if you are happy with

void __weak safe_udelay(unsigned long usecs)
{
	udelay(usecs);
}

and will have x86 have it's own safe_udelay...


Yinghai
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