From owner-freebsd-hackers  Fri Jul  6 15:27:51 2001
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Date: Fri, 06 Jul 2001 15:27:34 -0700 (PDT)
From: John Baldwin <jhb@FreeBSD.org>
To: Peter Pentchev <roam@orbitel.bg>
Subject: Re: LIST_NEXT()
Cc: freebsd-hackers@FreeBSD.ORG,
	Evan Sarmiento <kaworu@sektor7.ath.cx>
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On 06-Jul-01 Peter Pentchev wrote:
> On Fri, Jul 06, 2001 at 09:48:26AM -0400, Evan Sarmiento wrote:
>> Hello,
>> 
>> I'm writing a kernel module, and it involves traversing the proc list
>> searching for the right structure,
>> however, when I use SLIST_NEXT(p, p_list) in the program, I get a warning
>> when I compile it: 
>> 
>> warning: statement with mo effect
>> 
>> What am I doing wrong? I've read the manpages on queue and looked at the
>> proc structure.
>> 
>> Here's the code:
>> int
>> prfw_setflags(p, uap)
>> struct proc *p;
>> struct prfw_setflags_args *uap;
>> {
>> ...
>> if (uap->id) {
>>  while (uap->id != p->p_pid)
>>   LIST_NEXT(p, p_list);
>> }
> 
> Well, first, you're using LIST_NEXT(), not SLIST_NEXT() :)
> Second, none of the *_NEXT() queue.h macros modify their parameters;
> they just return a pointer to the next element.  So, just try:
> 
>       p = LIST_NEXT(p, p_list);
> 
> ..and you'll be just fine.

However, you should be using pfind() to look up a process by pid.

-- 

John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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