linux-kernel - Re: [PATCH] Turn rdmsr, rdtsc into inline functions, clarify names

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Date:	Sun, 6 Aug 2006 05:16:43 +0200
From:	Andi Kleen <ak@....de>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dmitry.torokhov@...il.com
Subject: Re: [PATCH] Turn rdmsr, rdtsc into inline functions, clarify names

> 	Please reconsider.  This isn't about being pretty, it's about not
> having hidden side-effects,

I wouldn't call it hidden, it's well defined in the architecture.

> and having typechecking.

The existing code will already reject any non integer and I don't
see a particular need to be more strict than that.

> > If you feel a need to clean up I would suggest you convert more
> > users over to the ll variants which take a single 64bit value
> > instead of two 32bit ones.
> 
> You mean the l and ll variants?  The 64 bit variants are rdmsrl and
> rdtscll, not to be confused with rdtscl, which returns the lower 32
> bits.  This confusion caused the x86_64 bug in gameport.c 

Why does gameport access MSRs or TSCs? That sounds like a bug in itself.

<looking at the code> 

This whole thing is broken, e.g. on a preemptive kernel when the
code can switch CPUs 

Dmitry, I would suggest to convert it over to do_gettimeofday and remove
all the architecture ifdefs.

Or maybe just remove it completely.  Who cares about the speed of a gameport 
anyways? And why can't they measure it in user space? 

> See why I want to fix these names?

No.

> So if you would prefer u64 rdtsc64(), u32 rdtsc_low(), u64 rdmsr64(int
> msr), u32 rdmsr_low(int msr), I can convert everyone to that, although
> it's a more invasive change...

I think things are most fine right now, except that I think most users
of high low should be converted to work directly on 64bit quantities.

-Andi
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