locking/atomic: Use s64 for atomic64_t on 64-bit

Now that all architectures use 64 consistently as the base type for the
atomic64 API, let's have the CONFIG_64BIT definition of atomic64_t use
s64 as the underlying type for atomic64_t, rather than long, matching
the generated headers.

On architectures where atomic64_read(v) is READ_ONCE(v->counter), this
patch will cause the return type of atomic64_read() to be s64.

As of this patch, the atomic64 API can be relied upon to consistently
return s64 where a value rather than boolean condition is returned. This
should make code more robust, and simpler, allowing for the removal of
casts previously required to ensure consistent types.

Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

include/linux/types.h

@@ -174,7 +174,7 @@ typedef struct {
 
 #ifdef CONFIG_64BIT
 typedef struct {
-	long counter;
+	s64 counter;
 } atomic64_t;
 #endif