locking/atomics: Switch to generated atomic-long

locking/atomics: Switch to generated atomic-long

As a step towards ensuring the atomic* APIs are consistent, let's switch
to wrappers generated by gen-atomic-long.h, using the same table that
gen-atomic-fallbacks.h uses to fill in gaps in the atomic_* and
atomic64_* APIs.

These are checked in rather than generated with Kbuild, since:

* This allows inspection of the atomics with git grep and ctags on a
  pristine tree, which Linus strongly prefers being able to do.

* The fallbacks are not affected by machine details or configuration
  options, so it is not necessary to regenerate them to take these into
  account.

* These are included by files required *very* early in the build process
  (e.g. for generating bounds.h), and we'd rather not complicate the
  top-level Kbuild file with dependencies.

Other than *_INIT() and *_cond_read_acquire(), all API functions are
implemented as static inline C functions, ensuring consistent type
promotion and/or truncation without requiring explicit casts to be
applied to parameters or return values.

Since we typedef atomic_long_t to either atomic_t or atomic64_t, we know
these types are equivalent, and don't require explicit casts between
them. However, as the try_cmpxchg*() functions take a pointer for the
'old' parameter, which may be an int or s64, an explicit cast is
generated for this.

There should be no functional change as a result of this patch (i.e.
existing code should not be affected). However, this introduces a number
of functions into the atomic_long_* API, bringing it into line with the
atomic_* and atomic64_* APIs.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com
Cc: linuxdrivers@attotech.com
Cc: dvyukov@google.com
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: aryabinin@virtuozzo.com
Cc: glider@google.com
Link: http://lkml.kernel.org/r/20180904104830.2975-4-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>