On 11/03/2010 11:13 AM, Eric Dumazet wrote:
> Le mercredi 03 novembre 2010 à 10:59 -0400, Jeremy Fitzhardinge a
> écrit :
>> From: Jeremy Fitzhardinge <[email protected]>
>>
>> If we don't need to use a locked inc for unlock, then implement it in C.
>>
>> Signed-off-by: Jeremy Fitzhardinge <[email protected]>
>> ---
>> arch/x86/include/asm/spinlock.h | 33 ++++++++++++++++++---------------
>> 1 files changed, 18 insertions(+), 15 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/spinlock.h
>> b/arch/x86/include/asm/spinlock.h
>> index 6711d36..082990a 100644
>> --- a/arch/x86/include/asm/spinlock.h
>> +++ b/arch/x86/include/asm/spinlock.h
>> @@ -33,9 +33,23 @@
>> * On PPro SMP or if we are using OOSTORE, we use a locked operation to
>> unlock
>> * (PPro errata 66, 92)
>> */
>> -# define UNLOCK_LOCK_PREFIX LOCK_PREFIX
>> +static __always_inline void __ticket_unlock_release(struct arch_spinlock
>> *lock)
>> +{
>> + if (sizeof(lock->tickets.head) == sizeof(u8))
>> + asm (LOCK_PREFIX "incb %0"
>> + : "+m" (lock->tickets.head) : : "memory");
>> + else
>> + asm (LOCK_PREFIX "incw %0"
>> + : "+m" (lock->tickets.head) : : "memory");
>> +
>> +}
>> #else
>> -# define UNLOCK_LOCK_PREFIX
>> +static __always_inline void __ticket_unlock_release(struct arch_spinlock
>> *lock)
>> +{
>> + barrier();
> technically speaking, it should be : smp_wmb()
Perhaps. In practise it won't make a difference because it is defined
as barrier() unless OOSTORE is defined, in which case we need to do a
locked increment anyway.
Thanks,
J
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