[PATCH 1/2] Generalised support for copy-on-write structures shared by threads.

[Bruce Evans]

On Sun, 3 May 2015, Julian Elischer wrote:

> On 5/2/15 12:56 AM, Mateusz Guzik wrote:
>> On Tue, Apr 28, 2015 at 06:45:01PM +1000, Bruce Evans wrote:
>>> On Tue, 28 Apr 2015, Mateusz Guzik wrote:
>>>> diff --git a/sys/sys/proc.h b/sys/sys/proc.h
>>>> index 64b99fc..f29d796 100644
>>>> --- a/sys/sys/proc.h
>>>> +++ b/sys/sys/proc.h
>>>> @@ -225,6 +225,7 @@ struct thread {
>>>> /* Cleared during fork1() */
>>>> #define	td_startzero td_flags
>>>> 	int		td_flags;	/* (t) TDF_* flags. */
>>>> +	u_int		td_cowgeneration;/* (k) Generation of COW pointers. 
>>>> */
>>>> 	int		td_inhibitors;	/* (t) Why can not run. */
>>>> 	int		td_pflags;	/* (k) Private thread (TDP_*) flags. 
>>>> */
>>>> 	int		td_dupfd;	/* (k) Ret value from fdopen. XXX */
>>> This name is so verbose that it messes up the comment indentation.
>>> 
>> Yeah, that's crap, but the naming is already inconsistent and verbose.
>> For instance there is td_generation alrady.
>> 
>> Is _cowgen variant ok?
> td_cowgen is much preferable  with comment  "(k) generation of c.o.w. 
> pointers."

> +	u_int		td_cowgen;	/* (k) generation of c.o.w. pointers. */

It is less preferable with such a comment.  The change in the comment just
adds 3 style bugs:
- inconsistent capitalization.  In this file, comments on struct members
   start with a capital letter
- punctuation for COW.  Acronyms are not punctuated.  Perhaps this one
   should be in lower case (like vm is usually in lower case).
- verboseness from the previous bug.  It expands the line line to 80.

But there is a problem with the comment.  It doesn't do much more than
echo the variable name with minor expansions and rearrangements.  The
only useful parts of it are "(k)" and "pointers".

Bruce