linux-kernel - Re: [PATCH v2 1/2] x86_32: summit_32, use BAD

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Date:	Wed, 25 Feb 2009 12:10:02 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	mingo@...hat.com, x86@...nel.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 1/2] x86_32: summit_32, use BAD_APICID


* Jiri Slaby <jirislaby@...il.com> wrote:

> On 24.2.2009 21:41, Jiri Slaby wrote:
>> --- a/arch/x86/kernel/apic/summit_32.c
>> +++ b/arch/x86/kernel/apic/summit_32.c
>> @@ -303,12 +303,10 @@ static inline unsigned int summit_cpu_mask_to_apicid(const cpumask_t *cpumask)
>>   	int cpu;
>>
>>   	num_bits_set = cpus_weight(*cpumask);
>> -	/* Return id to all */
>>   	if (num_bits_set>= nr_cpu_ids)
>> -		return 0xFF;
>> +		return BAD_APICID;
>
> Actually, wasn't this intended to return all available rather 
> than BAD (to which would correspond the comment), but 
> performed in a wrong manner? This is old code, any ideas who 
> would know this?
>
> In my opinion the check should be removed completely to allow 
> the code go through same-cluster check.
>
> In that case, the callers code is buggy, since it passes 
> online_cpu masks even on machines, where apics are not on the 
> same clusters.

It's most likely confusion in the old code. This used to be 
copy&paste-ed versions of different snapshots of the 
mach-default-code, hacked to make work on weird platforms. 
Mainline fixes/updates werent merged in consistently.

So could you please send a patch that fixes this?

	Ingo
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