Date: Fri, 22 Aug 2008 11:35:18 +0200
From: Andi Kleen <andi@firstfloor.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>, "H. Peter Anvin" <hpa@kernel.org>,
       Dave Jones <davej@redhat.com>, Vegard Nossum <vegard.nossum@gmail.com>,
       the arch/x86 maintainers <x86@kernel.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123	send_IPI_mask_bitmask+0xc3/0xe0()
Message-ID: <20080822093518.GK23334@one.firstfloor.org>
References: <19f34abd0808191251x4eb61c50n13ecf7c90f0f3d9f@mail.gmail.com> <20080820013930.GN9807@one.firstfloor.org> <19f34abd0808192326jc10e758m99e76bbd5714c5b8@mail.gmail.com> <20080822003659.GA7581@redhat.com> <48AE20B8.9000204@kernel.org> <20080822022841.GG23334@one.firstfloor.org> <48AE5BB8.5080701@zytor.com>
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> We still need the equivalent functionality, though.  The midlayer 
> (msr_on_cpu) may be pointless, but that doesn't change the fact that 
> putting this functionality in the lower layer (smp_call_function_single) 
> makes more sense.

Assuming you can actually have interrupts enabled at these point
and be otherwise ready to do call_function_simple (e.g. cpu hotplug
locking etc.) 

For a lot of MSR accesses in more complicated subsystems like cpufreq 
that requires complications.  I would think for many circumstances it's 
better to simply set affinity of the thread before at a higher level.

In hindsight I think it was my mistake to ever merge that.
I admit I never liked it, but just merged it because I wasn't able
to come up with a strong enough counter argument back then.

-Andi
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