linux-kernel - Re: [PATCH 1/8] cpumask: Replace cpumask_of_cpu with cpumask_of_cpu

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Message-ID: <48873D35.9030204@sgi.com>
Date:	Wed, 23 Jul 2008 07:16:21 -0700
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org,
	Len Brown <len.brown@...el.com>,
	Dave Jones <davej@...emonkey.org.uk>,
	Paul Jackson <pj@....com>,
	Tigran Aivazian <tigran@...azian.fsnet.co.uk>,
	Robert Richter <robert.richter@....com>,
	Greg Banks <gnb@....com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Adrian Bunk <bunk@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andreas Schwab <schwab@...e.de>,
	Johannes Weiner <hannes@...urebad.de>
Subject: Re: [PATCH 1/8] cpumask: Replace cpumask_of_cpu with	cpumask_of_cpu_ptr

Ingo Molnar wrote:
> * Rusty Russell <rusty@...tcorp.com.au> wrote:
> 
>>> I wouldn't mind it at all, and since it's almost always calling a 
>>> function that requires a cpumask_t pointer (like the cpu_* ops or 
>>> set_cpus_allowed_ptr) then there shouldn't be too many "pointer 
>>> dereference" penalties.  I'm just always a bit hesitant to make too 
>>> many generic changes since I have only x86 and ia64 machines to test 
>>> with.
>> The simple version is just a static array of [NR_CPUS] cpumask_t's.  
>> Do that, with an override for smarter archs?
>>
>> I really REALLY prefer that over the fairly tortuous macros.
> 
> a fresh commit in -git has exposed the topology.h mess - see the hack 
> below. We now have diverging versions of topology_core_siblings() 
> semantics - that sure cannot be right. Mike?
> 
> 	Ingo
> 
> ------->
> commit 695a6b456307455a10059512208e8ed0d376ecd3
> Author: Ingo Molnar <mingo@...e.hu>
> Date:   Wed Jul 23 13:19:44 2008 +0200
> 
>     topology: work around topology_core_siblings() breakage
>     
>     work around:
>     
>     drivers/net/sfc/efx.c: In function â€˜efx_probe_interrupts':
>     drivers/net/sfc/efx.c:845: error: lvalue required as unary â€˜&' operand
>     
>     the topology API is a mess right now ...
>     
>     Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
>  drivers/net/sfc/efx.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/sfc/efx.c b/drivers/net/sfc/efx.c
> index 45c72ee..1ababfa 100644
> --- a/drivers/net/sfc/efx.c
> +++ b/drivers/net/sfc/efx.c
> @@ -842,8 +842,10 @@ static void efx_probe_interrupts(struct efx_nic *efx)
>  			for_each_online_cpu(cpu) {
>  				if (!cpu_isset(cpu, core_mask)) {
>  					++efx->rss_queues;
> +#if 0
>  					cpus_or(core_mask, core_mask,
>  						topology_core_siblings(cpu));
> +#endif
>  				}
>  			}
>  		} else {

Ahh, yes, I see it now.  If you don't define topology_core_siblings then you get:

#ifndef topology_core_siblings
#define topology_core_siblings(cpu)             cpumask_of_cpu(cpu)
#endif

And of course this is no longer an lvalue.

Rusty - if you don't think there'll be objections from other arches I can put in
a generic cpumask_of_cpu_map[].

Thanks,
Mike



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