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SubjectRe: [x86] Unify semaphore_32.S and rwlock_64.S
On 01/20/2010 04:46 PM, Linus Torvalds wrote:
>
>
> On Wed, 20 Jan 2010, Linus Torvalds wrote:
>>
>> #define RWSEM_UNLOCKED_VALUE 0x00000000
>> #define RWSEM_ACTIVE_BIAS 0x00000001
>> #define RWSEM_ACTIVE_MASK 0x3fffffff
>> #define RWSEM_WAITING_BIAS (~RWSEM_ACTIVE_MASK)
>> #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
>> #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
>
> Btw, doing that RWSEM_WAITING_BIAS cleanup (we currently have it as an
> independent constant) means that now all constants are shared except for
> that RWSEM_ACTIVE_MASK. So it ends up being something like this:
>
> #ifdef CONFIG_RWSEM_64bit
> typedef __s64 rwsem_count_t;
> #define RWSEM_ACTIVE_MASK 0x3fffffff
> #else
> typedef __s32 rwsem_count_t;
> #define RWSEM_ACTIVE_MASK 0xffff
> #endif
>
> #define RWSEM_UNLOCKED_VALUE 0x00000000
> #define RWSEM_ACTIVE_BIAS 0x00000001
> #define RWSEM_WAITING_BIAS (~RWSEM_ACTIVE_MASK)
> #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
> #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
>
> with just that two-line difference for the 32-bit/64-bit case.
>
> At least I _think_ so.
>

Yes, I already had that change in my tree (or rather, I wrote it as
(-RWSEM_ACTIVE_MASK-1) to be consistent with what was previously there,
but (~RWSEM_ACTIVE_MASK) makes more sense.)

> And it's worth noting (again) that I didn't actually push the
> twsem_count_t changes down into the slow-path code in lib/rwsem.c. There's
> a few variables there that might need looking at too. I _think_ they are
> all ok as-is (unlike the header file, lib/rwsem.c seems to consistently
> use 'signed long' rather than mix 32-bit and 64-bit types), but it migh be
> cleaner to make them rwsem_count_t's too.

Yes, if we have it we should it consistently.

-hpa



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