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SubjectRe: [PATCH] locking/qrwlock: Let qrwlock has same layout regardless of the endian


On 2016年06月15日 17:20, Will Deacon wrote:
> On Wed, Jun 15, 2016 at 05:16:17PM +0800, Pan Xinhui wrote:
>> This patch aims to get rid of endianness in queued_write_unlock(). We
>> want to set __qrwlock->wmode to NULL, however the address is not
>> &lock->cnts in big endian machine. That causes queued_write_unlock()
>> write NULL to the wrong field of __qrwlock.
>>
>> Actually qrwlock can have same layout, IOW we can remove the #if
>> __little_endian in struct __qrwlock. With such modification, we only
>> need define some _QW* and _QR* with corresponding values in different
>> endian systems.
>>
>> Suggested-by: Will Deacon <will.deacon@arm.com>
>> Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
>> ---
>> include/asm-generic/qrwlock.h | 15 +++++++++++----
>> kernel/locking/qrwlock.c | 10 ++++------
>> 2 files changed, 15 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
>> index 54a8e65..b135c11 100644
>> --- a/include/asm-generic/qrwlock.h
>> +++ b/include/asm-generic/qrwlock.h
>> @@ -27,11 +27,18 @@
>> /*
>> * Writer states & reader shift and bias
>> */
>> -#define _QW_WAITING 1 /* A writer is waiting */
>> -#define _QW_LOCKED 0xff /* A writer holds the lock */
>> -#define _QW_WMASK 0xff /* Writer mask */
>> +#ifdef __LITTLE_ENDIAN
>> #define _QR_SHIFT 8 /* Reader count shift */
>> -#define _QR_BIAS (1U << _QR_SHIFT)
>> +#define _QW_SHIFF 0 /* Writer mode shift */
>
> Well, there are other typos that could've been worse, but you probably
> want to fix this...
>
oh... I am really in rush. sorry. will fix it and seed patch v2 soon.

thank you for pointing it out.

> Will
>

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