linux-kernel - Re: [gcv v4 05/38] percpu: Add preemption checks to __this

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Message-ID: <20130916103052.GB29018@twins.programming.kicks-ass.net>
Date:	Mon, 16 Sep 2013 12:30:52 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org,
	linux-arch@...r.kernel.org, Steven Rostedt <srostedt@...hat.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [gcv v4 05/38] percpu: Add preemption checks to __this_cpu ops

On Tue, Sep 03, 2013 at 10:33:20PM +0000, Christoph Lameter wrote:
> We define a check function in order to avoid trouble with the
> include files. Then the higher level __this_cpu macros are
> modified to involve the check before any operation.
> 

So this_cpu_ptr() is the one with the check, and __this_cpu_ptr() is the
one without. But for the other this_cpu ops __this_cpu_$OP() is going to
be the one with a check and this_cpu_$OP() the one without?

Sounds like a bloody marvelous idea :/



> Index: linux/include/linux/percpu.h
> ===================================================================
> --- linux.orig/include/linux/percpu.h	2013-09-03 13:38:49.818888738 -0500
> +++ linux/include/linux/percpu.h	2013-09-03 13:38:49.810888819 -0500
> @@ -172,6 +172,12 @@ extern phys_addr_t per_cpu_ptr_to_phys(v
>  
>  extern void __bad_size_call_parameter(void);
>  
> +#ifdef CONFIG_PREEMPT
> +extern void this_cpu_preempt_check(void);
> +#else
> +static inline void this_cpu_preempt_check(void) { }
> +#endif

How about re-using debug_smp_processor_id() instead?
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