From mboxrd@z Thu Jan  1 00:00:00 1970
From: Cyril Hrubis <chrubis@suse.cz>
Date: Wed, 13 Apr 2016 15:59:58 +0200
Subject: [LTP] [PATCH 3/4] tst_atomic: add atomic_add_return for x86/64,
 ppc/64 and s390/x
In-Reply-To: <7862473e97588497afd83d52937c5f3fc5aac120.1460552890.git.jstancek@redhat.com>
References: <82bcc056edc64dee3a13275a2b4bdbec958f60eb.1460552890.git.jstancek@redhat.com>
 <7862473e97588497afd83d52937c5f3fc5aac120.1460552890.git.jstancek@redhat.com>
Message-ID: <20160413135957.GA11529@rei.lan>
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To: ltp@lists.linux.it

Hi!
> +#if defined(__i386__) || defined(__x86_64__)
> +#define HAVE_ATOMIC_ADD_RETURN 1
> +extern void __xadd_wrong_size(void);
> +static inline __attribute__((always_inline)) int atomic_add_return(int i, int *v)
> +{
> +	int __ret = i;
> +
> +	switch (sizeof(*v)) {
> +	case 1:
> +		asm volatile ("lock; xaddb %b0, %1\n"
> +			: "+q" (__ret), "+m" (*v) : : "memory", "cc");
> +		break;
> +	case 2:
> +		asm volatile ("lock; xaddw %w0, %1\n"
> +			: "+r" (__ret), "+m" (*v) : : "memory", "cc");
> +		break;

Do we really need byte and word version? As far as I can tell int is 4
bytes on x86 and x86_64 and unlike kernel where this is a macro we
cannot pass anything else than int.

> +	case 4:
> +		asm volatile ("lock; xaddl %0, %1\n"
> +			: "+r" (__ret), "+m" (*v) : : "memory", "cc");
> +		break;
> +	case 8:
> +		asm volatile ("lock; xaddq %q0, %1\n"
> +			: "+r" (__ret), "+m" (*v) : : "memory", "cc");
> +		break;

The same goes for the quad version here.

> +	default:
> +		__xadd_wrong_size();

So this supposedly causes linker error by trying to link nonexistent
function, right?

I guess that we should either add nonexistent to the function name or
short commment with explanation.

Also it should start with tst_ in order to avoid teoretical collisions
with system functions.

> +	}
> +	return i + __ret;
> +}
> +#endif
> +
> +#if defined(__powerpc__) || defined(__powerpc64__)
> +#define HAVE_ATOMIC_ADD_RETURN 1
> +static inline __attribute__((always_inline)) int atomic_add_return(int i, int *v)
> +{
> +	int t;
> +
> +	asm volatile(
> +		"	sync\n"
> +		"1:	lwarx	%0,0,%2		# atomic_add_return\n"
> +		"	add %0,%1,%0\n"
> +		"	stwcx.	%0,0,%2 \n"
> +		"	bne-	1b\n"
> +		"	sync\n"
> +		: "=&r" (t)
> +		: "r" (i), "r" (v)
> +		: "cc", "memory");
> +	return t;
> +}
> +#endif
> +
> +#if defined(__s390__) || defined(__s390x__)
> +#define HAVE_ATOMIC_ADD_RETURN 1
> +static inline __attribute__((always_inline)) int atomic_add_return(int i, int *v)
> +{
> +	int old_val, new_val;
> +
> +	asm volatile(
> +		"	l	%0,%2\n"
> +		"0:	lr	%1,%0\n"
> +		"	ar	%1,%3\n"
> +		"	cs	%0,%1,%2\n"
> +		"	jl	0b"
> +		: "=&d" (old_val), "=&d" (new_val), "+Q" (*v)
> +		: "d" (i)
> +		: "cc", "memory");
> +	return old_val + i;
> +}
> +#endif
> +#endif /* HAVE_SYNC_ADD_AND_FETCH == 1 */
> +
> +#if !defined(HAVE_ATOMIC_ADD_RETURN)
>  #error Your compiler does not provide __sync_add_and_fetch and LTP\
>   implementation is missing for your architecture.
>  #endif

-- 
Cyril Hrubis
chrubis@suse.cz