Date: Tue, 21 Apr 2020 19:44:36 -0700 From: Benjamin Kaduk <kaduk@mit.edu> To: Yuri Pankov <ypankov@fastmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: "most interesting" process in w(1) Message-ID: <20200422024436.GA27494@kduck.mit.edu> In-Reply-To: <b43e40b2-c2a0-cf55-a932-ab2e0cefdcdb@fastmail.com> References: <b43e40b2-c2a0-cf55-a932-ab2e0cefdcdb@fastmail.com>
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On Wed, Apr 22, 2020 at 12:09:48AM +0300, Yuri Pankov wrote:
> Looking at how w(1) finds "most interesting" process for terminal, I
> noticed the following code which looks strange to me (usr.bin/w/w.c,
> line 360 in HEAD)
>
> for (ep = ehead; ep != NULL; ep = ep->next) {
> if (ep->tdev == kp->ki_tdev) {
> /*
> * proc is associated with this terminal
> */
> if (ep->kp == NULL && kp->ki_pgid == kp->ki_tpgid) {
> /*
> * Proc is 'most interesting'
> */
> if (proc_compare(ep->kp, kp))
> ep->kp = kp;
> ...
> }
> }
> }
>
> Given the (ep->kp == NULL) check, proc_compare() becomes no-op, it will
> always select kp, and that's the only place we ever set ep->kp, so the
> first matching process is always "most interesting". If that's really
> what we want, we could do without the proc_compare() call. What am I
> missing here?
I suspect it makes more sense as a "!=" than a "==" (with ep->kp = kp;
always occurring for the "== NULL" case).
-Ben
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