[PATCH] hlist_for_each_safe cleanup

[PATCH] hlist_for_each_safe cleanup

[Stephen Hemminger]

Make code for hlist_for_each_safe use better code (same as hlist_for_each_entry_safe).
Get rid of comment about prefetch, because that was fixed a while ago.
Only current use of this is in the bridge code, that I maintain.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>

--- linux-2.6/include/linux/list.h	2004-07-23 09:36:18.000000000 -0700
+++ tcp-2.6/include/linux/list.h	2004-07-23 11:43:25.000000000 -0700
@@ -620,13 +620,12 @@
 
 #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
 
-/* Cannot easily do prefetch unfortunately */
 #define hlist_for_each(pos, head) \
 	for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
 	     pos = pos->next)
 
 #define hlist_for_each_safe(pos, n, head) \
-	for (pos = (head)->first; n = pos ? pos->next : NULL, pos; \
+	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
 	     pos = n)
 
 /**

Re: [PATCH] hlist_for_each_safe cleanup

[Andreas Schwab]

Stephen Hemminger <shemminger@osdl.org> writes:

> --- linux-2.6/include/linux/list.h	2004-07-23 09:36:18.000000000 -0700
> +++ tcp-2.6/include/linux/list.h	2004-07-23 11:43:25.000000000 -0700
> @@ -620,13 +620,12 @@
>  
>  #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
>  
> -/* Cannot easily do prefetch unfortunately */
>  #define hlist_for_each(pos, head) \
>  	for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
>  	     pos = pos->next)
>  
>  #define hlist_for_each_safe(pos, n, head) \
> -	for (pos = (head)->first; n = pos ? pos->next : NULL, pos; \
> +	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \

What's wrong with using the comma operator instead of non-standard
statement expressions?

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH] hlist_for_each_safe cleanup

[Stephen Hemminger]

On Fri, 23 Jul 2004 23:22:23 +0200
Andreas Schwab <schwab@suse.de> wrote:

> Stephen Hemminger <shemminger@osdl.org> writes:
> 
> > --- linux-2.6/include/linux/list.h	2004-07-23 09:36:18.000000000 -0700
> > +++ tcp-2.6/include/linux/list.h	2004-07-23 11:43:25.000000000 -0700
> > @@ -620,13 +620,12 @@
> >  
> >  #define hlist_entry(ptr, type, member) container_of(ptr,type,member)
> >  
> > -/* Cannot easily do prefetch unfortunately */
> >  #define hlist_for_each(pos, head) \
> >  	for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
> >  	     pos = pos->next)
> >  
> >  #define hlist_for_each_safe(pos, n, head) \
> > -	for (pos = (head)->first; n = pos ? pos->next : NULL, pos; \
> > +	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
> 
> What's wrong with using the comma operator instead of non-standard
> statement expressions?

It was more a case of consistency and avoiding the n = NULL assignment when pos
is NULL.  

Look at hlist_for_each_entry_safe

#define hlist_for_each_entry_safe(tpos, pos, n, head, member)            \
        for (pos = (head)->first;                                        \
             pos && ({ n = pos->next; 1; }) &&                           \
                ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
             pos = n)


What's your problem with the gcc extensions, the kernel uses them all over the place,
planning on starting a conversion?

Re: [PATCH] hlist_for_each_safe cleanup

[Andreas Schwab]

Stephen Hemminger <shemminger@osdl.org> writes:

> What's your problem with the gcc extensions, the kernel uses them all over the place,
> planning on starting a conversion?

Why use an extension when an equivalent standard construct exists that is
no less readable?

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH] hlist_for_each_safe cleanup

[Herbert Xu]

Stephen Hemminger <shemminger@osdl.org> wrote:
> On Fri, 23 Jul 2004 23:22:23 +0200
>
>> What's wrong with using the comma operator instead of non-standard
>> statement expressions?
> 
> It was more a case of consistency and avoiding the n = NULL assignment when pos
> is NULL.  
> 
> Look at hlist_for_each_entry_safe
> 
> #define hlist_for_each_entry_safe(tpos, pos, n, head, member)            \
>        for (pos = (head)->first;                                        \
>             pos && ({ n = pos->next; 1; }) &&                           \
>                ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
>             pos = n)
> 
> What's your problem with the gcc extensions, the kernel uses them all over the place,
> planning on starting a conversion?

Yes but a comma operator will achieve exactly the same thing and is
more concise:

pos && (n = pos->next, 1) &&

You could also write

pos && ((n = pos->next) || 1) &&

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
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