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SubjectRe: [tip:locking/core] locking/atomics: Simplify the op definitions in atomic.h some more

* Peter Zijlstra <peterz@infradead.org> wrote:

> And if we're going to do codegen, we might as well all generate this
> anyway, so all this mucking about is a complete waste of time.

I'm not yet convinced that it will be cleaner, but can be convinced in principle,
but meanwhile the existing code is arguably butt-ugly and bloaty.

Regarding these cleanups, we had this before:

/* atomic_add_return_relaxed */
#ifndef atomic_add_return_relaxed
#define atomic_add_return_relaxed atomic_add_return
#define atomic_add_return_acquire atomic_add_return
#define atomic_add_return_release atomic_add_return

#else /* atomic_add_return_relaxed */

#ifndef atomic_add_return_acquire
#define atomic_add_return_acquire(...) \
__atomic_op_acquire(atomic_add_return, __VA_ARGS__)
#endif

#ifndef atomic_add_return_release
#define atomic_add_return_release(...) \
__atomic_op_release(atomic_add_return, __VA_ARGS__)
#endif

#ifndef atomic_add_return
#define atomic_add_return(...) \
__atomic_op_fence(atomic_add_return, __VA_ARGS__)
#endif
#endif /* atomic_add_return_relaxed */

Which is 23 lines per definition.

Now we have this much more compact definition:

#ifndef atomic_add_return_relaxed
# define atomic_add_return_relaxed atomic_add_return
# define atomic_add_return_acquire atomic_add_return
# define atomic_add_return_release atomic_add_return
#else
# ifndef atomic_add_return
# define atomic_add_return(...) __op_fence(atomic_add_return, __VA_ARGS__)
# define atomic_add_return_acquire(...) __op_acquire(atomic_add_return, __VA_ARGS__)
# define atomic_add_return_release(...) __op_release(atomic_add_return, __VA_ARGS__)
# endif
#endif

Which is just _half_ the linecount.

Automated code generation might improve this some more, but the net effect on the
core <linux/atomic.h> code right now is 373 lines removed:

include/linux/atomic.h | 1109 ++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------------------------------------------------------------------------------
1 file changed, 368 insertions(+), 741 deletions(-)

... <linux/atomic.h> shrunk to just 709 lines.

The x86/include/asm/atomic64_64.h file got smaller as well due to the cleanups:

arch/x86/include/asm/atomic64_64.h | 216 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----------------------------------------------------------------------------
1 file changed, 97 insertions(+), 119 deletions(-)

So unless you can clean this up and shrink this even more, these changes are
obviously justified on their own.

Thanks,

Ingo

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