Hi,
On Tue, Mar 28, 2017 at 06:15:41PM +0200, Dmitry Vyukov wrote:
> The new header allows to wrap per-arch atomic operations
> and add common functionality to all of them.
I had a quick look at what it would take to have arm64 use this, and I
have a couple of thoughts.
> +static __always_inline int atomic_xchg(atomic_t *v, int i)
> +{
> + return arch_atomic_xchg(v, i);
> +}
I generally agree that avoiding several layers of CPP aids readability
here, and as-is I think this is fine.
However, avoiding CPP entirely will mean that the file becomes painfully
verbose when support for {relaxed,acquire,release}-order variants is
added.
Just considering atomic_xchg{,_relaxed,_acquire,_release}(), for
example:
----
static __always_inline int atomic_xchg(atomic_t *v, int i)
{
kasan_check_write(v, sizeof(*v));
return arch_atomic_xchg(v, i);
}
#ifdef arch_atomic_xchg_relaxed
static __always_inline int atomic_xchg(atomic_t *v, int i)
{
kasan_check_write(v, sizeof(*v));
return arch_atomic_xchg_relaxed(v, i);
}
#define atomic_xchg_relaxed atomic_xchg_relaxed
#endif
#ifdef arch_atomic_xchg_acquire
static __always_inline int atomic_xchg(atomic_t *v, int i)
{
kasan_check_write(v, sizeof(*v));
return arch_atomic_xchg_acquire(v, i);
}
#define atomic_xchg_acquire atomic_xchg_acquire
#endif
#ifdef arch_atomic_xchg_release
static __always_inline int atomic_xchg(atomic_t *v, int i)
{
kasan_check_write(v, sizeof(*v));
return arch_atomic_xchg_release(v, i);
}
#define atomic_xchg_release atomic_xchg_release
#endif
----
With some minimal CPP, it can be a lot more manageable:
----
#define INSTR_ATOMIC_XCHG(order) \
static __always_inline int atomic_xchg##order(atomic_t *v, int i) \
{ \
kasan_check_write(v, sizeof(*v)); \
arch_atomic_xchg##order(v, i); \
}
#define INSTR_ATOMIC_XCHG()
#ifdef arch_atomic_xchg_relaxed
INSTR_ATOMIC_XCHG(_relaxed)
#define atomic_xchg_relaxed atomic_xchg_relaxed
#endif
#ifdef arch_atomic_xchg_acquire
INSTR_ATOMIC_XCHG(_acquire)
#define atomic_xchg_acquire atomic_xchg_acquire
#endif
#ifdef arch_atomic_xchg_relaxed
INSTR_ATOMIC_XCHG(_relaxed)
#define atomic_xchg_relaxed atomic_xchg_relaxed
#endif
----
Is there any objection to some light CPP usage as above for adding the
{relaxed,acquire,release} variants?
Thanks,
Mark.
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