linux-kernel - Re: [PATCH 1/10] Add generic helpers for arch IPI function calls

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Message-ID: <20080507204251.GO16217@kernel.dk>
Date:	Wed, 7 May 2008 22:42:52 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Nick Piggin <npiggin@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	jeremy@...p.org, mingo@...e.hu
Subject: Re: [PATCH 1/10] Add generic helpers for arch IPI function calls

On Mon, May 05 2008, Paul E. McKenney wrote:
> OK.  The below still permits parallel smp_call_function()
> and smp_call_function_mask() as well as permitting parallel
> smp_call_function_single().  It prohibits the irq-disabled case.
> 
> Thoughts?

Sorry for the delayed response here. The below looks pretty good to me,
though it'll require a few modifications to fixup smp_call_function()
from irq disabled context.

But that's doable, though I have to do a grep over the kernel to check
everything (I remember CPU send_stop being one such path). Not a huge
fan of such an interface, but hey...

Is everyone OK with going this route, initially at least? It's the
lesser of all evils, I think.

> diff --git a/arch/Kconfig b/arch/Kconfig
> index a5a0184..5ae9360 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -38,4 +38,4 @@ config HAVE_KRETPROBES
>  	def_bool n
>  
>  config USE_GENERIC_SMP_HELPERS
> -	def_bool n
> +	def_bool y

This part puzzled me, why? We default to 'n' and let converted archs
opt-in, so I don't get this part of your patch...

-- 
Jens Axboe

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