On 10/01/2013 12:11 AM, Will Deacon wrote:

On Sun, Sep 29, 2013 at 04:52:28AM +0100, Chen Gang wrote:

quoted

"arc/arm" will be never on 64-bit, it is mainly on 32-bit (may also can
be on 16-bit).

So better to use 'int' instead of 'unsigned long' for normal register
variable (on 16-bit, 'int' is allowed to be 16-bit, so historically,
often use 'int' for normal register variables).

This commit message doesn't make a blind bit of sense! arch/arm/ is a 32-bit
architecture in the sense that int will always be 32-bit there. This patch
is just a cosmetic change, bringing our atomic_t manipulation code inline
with the atomic_t type definition.

OK, thanks. That means: "arm means arm 32-bit, arm64 means arm 64-bit.
The current Linux kernel main line does not support arm 16-bit".

Since "bringing our atomic_t ... with the atomic_t type definition", can
we use 'atomic_t" instead of 'unsigned long'?

And can we use 'atomic64_t" instead of 'unsigned long' in atomic64_*()?

quoted

@@ -297,7 +297,7 @@ static inline void atomic64_set(atomic64_t *v, long

long i)
 static inline void atomic64_add(long long i, atomic64_t *v)
 {
 	long long result;
-	unsigned long tmp;
+	int tmp;

Please leave the atomic64_* functions alone here; the reasoning I explained
above doesn't apply to them. Whilst int may work, it seems gratuitous to
make this change for no reason.

For 32-bit, it seems we can not use 'atomic64_t' instead of 'unsigned
long' in atomic64_*().  ;-)

For 32-bit, the original 'unsigned long' in atomic64_add() is correct,
or is also a bug?

Will

In fact, if arm only for 32-bit, I really don't know why we need 'int'
instead of some 'unsigned long' (neither can let patch comment correct,
nor know which 'unsigned long' need be instead of).  :-(

It seems we need be careful to not let this patch make new bug for arm.



Thanks.
-- 
Chen Gang