[ltt-dev] [PATCH 1/2] use generic-size operations for common implementation of atomic ops

[compudj@krystal.dyndns.org (Mathieu Desnoyers)]

* Paolo Bonzini (pbonzini at redhat.com) wrote:
> The definition of _uatomic_cmpxchg is different in x86 and other architectures.
> For x86 it is a 4-argument macro, for other architectures it is a 3-argument
> function.  The next patch will use uatomic_cmpxchg in uatomic_generic.h
> even on x86: adjust existing uses of the underscore-prefixed variant for
> consistency.

Nope. See 

#if ((BITS_PER_LONG != 64) && defined(CONFIG_RCU_COMPAT_ARCH))

#else

path in uatomic_arch_x86.h

to see why we use this trick.

We remove a dynamic test on these architectures where compatibility mode
is present.

Thanks,

Mathieu

> 
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> ---
>  urcu/uatomic_generic.h |   24 ++++++++++++++++--------
>  1 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/urcu/uatomic_generic.h b/urcu/uatomic_generic.h
> index f65b398..383ddfa 100644
> --- a/urcu/uatomic_generic.h
> +++ b/urcu/uatomic_generic.h
> @@ -201,7 +201,8 @@ unsigned long _uatomic_add_return(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned char *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, old + val, 1);
> +			oldt = uatomic_cmpxchg((unsigned char *)addr,
> +                                               old, old + val);
>  		} while (oldt != old);
>  
>  		return old + val;
> @@ -215,7 +216,8 @@ unsigned long _uatomic_add_return(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned short *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, old + val, 2);
> +			oldt = uatomic_cmpxchg((unsigned short *)addr,
> +                                               old, old + val);
>  		} while (oldt != old);
>  
>  		return old + val;
> @@ -228,7 +230,8 @@ unsigned long _uatomic_add_return(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned int *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, old + val, 4);
> +			oldt = uatomic_cmpxchg((unsigned int *)addr,
> +                                               old, old + val);
>  		} while (oldt != old);
>  
>  		return old + val;
> @@ -241,7 +244,8 @@ unsigned long _uatomic_add_return(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned long *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, old + val, 8);
> +			oldt = uatomic_cmpxchg((unsigned long *)addr,
> +                                               old, old + val);
>  		} while (oldt != old);
>  
>  		return old + val;
> @@ -273,7 +277,8 @@ unsigned long _uatomic_exchange(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned char *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, val, 1);
> +			oldt = uatomic_cmpxchg((unsigned char *)addr,
> +                                               old, val);
>  		} while (oldt != old);
>  
>  		return old;
> @@ -287,7 +292,8 @@ unsigned long _uatomic_exchange(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned short *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, val, 2);
> +			oldt = uatomic_cmpxchg((unsigned short *)addr,
> +                                               old, val);
>  		} while (oldt != old);
>  
>  		return old;
> @@ -300,7 +306,8 @@ unsigned long _uatomic_exchange(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned int *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, val, 4);
> +			oldt = uatomic_cmpxchg((unsigned int *)addr,
> +                                               old, val);
>  		} while (oldt != old);
>  
>  		return old;
> @@ -313,7 +320,8 @@ unsigned long _uatomic_exchange(void *addr, unsigned long val, int len)
>  		oldt = uatomic_read((unsigned long *)addr);
>  		do {
>  			old = oldt;
> -			oldt = _uatomic_cmpxchg(addr, old, val, 8);
> +			oldt = uatomic_cmpxchg((unsigned long *)addr,
> +                                               old, val);
>  		} while (oldt != old);
>  
>  		return old;
> -- 
> 1.7.3.2
> 
> 
> 
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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com