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Date: Fri, 12 Nov 2010 08:27:04 -0800
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: vatsa@linux.vnet.ibm.com
CC: Peter Zijlstra <peterz@infradead.org>,
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        Nick Piggin <npiggin@suse.de>, Jan Beulich <JBeulich@novell.com>,
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        "H. Peter Anvin" <hpa@zytor.com>,
        Linux Virtualization <virtualization@lists.linux-foundation.org>,
        Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Subject: Re: [PATCH 04/20] x86/ticketlock: make large and small ticket versions
 of spin_lock the same
References: <cover.1288794124.git.jeremy.fitzhardinge@citrix.com> <5b3cbff3a6e96a085651f140a0525be80a4df8ba.1288794124.git.jeremy.fitzhardinge@citrix.com> <20101112121932.GA30016@linux.vnet.ibm.com>
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On 11/12/2010 04:19 AM, Srivatsa Vaddagiri wrote:
> On Wed, Nov 03, 2010 at 10:59:45AM -0400, Jeremy Fitzhardinge wrote:
>> Make the bulk of __ticket_spin_lock look identical for large and small
>> number of cpus.
> [snip]
>
>>  #if (NR_CPUS < 256)
>>  static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
>>  {
>> -	register union {
>> -		struct __raw_tickets tickets;
>> -		unsigned short slock;
>> -	} inc = { .slock = 1 << TICKET_SHIFT };
>> +	register struct __raw_tickets inc = { .tail = 1 };
> [snip]
>
>>  #else
>>  static __always_inline void __ticket_spin_lock(arch_spinlock_t *lock)
>>  {
>> -	unsigned inc = 1 << TICKET_SHIFT;
>> -	__ticket_t tmp;
>> +	register struct __raw_tickets inc = { .tickets.tail = 1 };
> s/.tickets//?
>
> Otherwise I get a compile error for NR_CPUS > 256, with just 4 patches applied.

Yeah, likely.  That's precisely why I wanted to make them the same ;).

    J