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Date: Fri, 20 Jul 2001 09:00:00 -0700
From: Julian Elischer <julian@elischer.org>
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To: current@freebsd.org
Subject: Re: huh? in Selrecord(): what is this for?
References: <3B5854E3.B6D9C86D@elischer.org>
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Never mind.. I'm an ijut...

Julian Elischer wrote:
> 
> void
> selrecord(selector, sip)
>         struct proc *selector;
>         struct selinfo *sip;
> {
>         struct proc *p;
>         pid_t mypid;
> 
>         mypid = selector->p_pid;
>         if (sip->si_pid == mypid)
>                 return;
>         if (sip->si_pid && (p = pfind(sip->si_pid))) {
> 
> Why do we look up 'p' when we got it as an argument?
> (race condition detection?)
> 
> (I'm modifying things for threads so I came up against this....)
> 
>                 mtx_lock_spin(&sched_lock);
>                 if (p->p_wchan == (caddr_t)&selwait) {
>                         mtx_unlock_spin(&sched_lock);
>                         PROC_UNLOCK(p);
>                         sip->si_flags |= SI_COLL;
>                         return;
>                 }
>                 mtx_unlock_spin(&sched_lock);
>                 PROC_UNLOCK(p);
>         }
>         sip->si_pid = mypid;
> }
> --
> +------------------------------------+       ______ _  __
> |   __--_|\  Julian Elischer         |       \     U \/ / hard at work in
> |  /       \ julian@elischer.org     +------>x   USA    \ a very strange
> | (   OZ    )                                \___   ___ | country !
> +- X_.---._/    presently in San Francisco       \_/   \\
>           v

-- 
+------------------------------------+       ______ _  __
|   __--_|\  Julian Elischer         |       \     U \/ / hard at work in 
|  /       \ julian@elischer.org     +------>x   USA    \ a very strange
| (   OZ    )                                \___   ___ | country !
+- X_.---._/    presently in San Francisco       \_/   \\
          v

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