linux-kernel - Re: [PATCH 4/4, v2] x86: enlightenment for ticket spin locks

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Date:	Wed, 30 Jun 2010 12:22:16 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Ky Srinivasan" <KSrinivasan@...ell.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH 4/4, v2] x86: enlightenment for ticket spin locks
	 -	 improve yield behavior on Xen

>>> On 30.06.10 at 12:08, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> On 06/29/2010 04:35 PM, Jan Beulich wrote:
>> --- 2.6.35-rc3-virt-spinlocks.orig/arch/x86/include/asm/spinlock.h
>> +++ 2.6.35-rc3-virt-spinlocks/arch/x86/include/asm/spinlock.h
>> @@ -85,6 +85,15 @@ extern void virt_spin_unlock_stub(void);
>>  # define UNLOCK_LOCK_PREFIX
>>  #endif
>>  
>> +static __always_inline void __ticket_spin_set_owner(arch_spinlock_t *lock,
>> +                                                    int owned)
>> +{
>> +#ifdef CONFIG_ENLIGHTEN_SPINLOCKS
>> +	if (owned)
>> +		lock->owner = percpu_read(cpu_number);
>>   
> 
> Why not smp_processor_id()?  Is this different in some way?

Including the respective header here just doesn't work due to
resulting cyclic dependencies.

Jan

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