linux-kernel - Re: [PATCH 9/11] Panic delay fix

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Message-ID: <d120d5000702080643k453e73e3h6d481f9d65a4e856@mail.gmail.com>
Date:	Thu, 8 Feb 2007 09:43:56 -0500
From:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
To:	"Rusty Russell" <rusty@...tcorp.com.au>
Cc:	"Pavel Machek" <pavel@....cz>, "Zachary Amsden" <zach@...are.com>,
	"Andi Kleen" <ak@....de>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...l.org>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"Chris Wright" <chrisw@...s-sol.org>
Subject: Re: [PATCH 9/11] Panic delay fix

On 2/7/07, Rusty Russell <rusty@...tcorp.com.au> wrote:
> On Wed, 2007-02-07 at 12:35 +0000, Pavel Machek wrote:
> > Ugh, it sounds like paravirt is more b0rken then I thought. It should
> > always to the proper delay, then replace those udelays that are not
> > needed on virtualized hardware with something else.
> >
> > Just magically defining udelay into nop is broken.
>
> We'd have to audit and figure out what udelays are for hardware and
> which are not, but the evidence is that the vast majority of them are
> for hardware and not needed for virtualization.
>
> Changing udelay to "hardware_udelay" or something all over the kernel
> would have delayed the paravirt_ops merge by an infinite amount 8)
>

However I am not really fond of idea of adding constructs like this
all over the code:

#define USE_REAL_TIME_DELAY_I_REALLY_MEAN_IT_THIS_TIME_I_SWEAR

as the time passes... Drivers should be blissfully ignorant of being
run on virtual hardware.

-- 
Dmitry
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