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From: arisawa <arisawa@ar.aichi-u.ac.jp>
In-Reply-To: <CAOw7k5j24zwQtNit8jZ-j0m+A6semHwM5kQ6C5t7q9m6uVafzA@mail.gmail.com>
Date: Thu, 29 Jan 2015 12:57:24 +0900
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References: <CAOw7k5hocVshTBBvXA86x91PpZ1hBBdAbMUBao+vCGL2wH9ryw@mail.gmail.com>
	<abaa51d009b85e94623f723606bc2ccb@felloff.net>
	<CAOw7k5j24zwQtNit8jZ-j0m+A6semHwM5kQ6C5t7q9m6uVafzA@mail.gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] protection against resource exhaustion
Topicbox-Message-UUID: 3d5faeb4-ead9-11e9-9d60-3106f5b1d025

Thanks for all.

I have looked old source code /sys/src/9/port/proc.c, and found the next =
code exists from very old day.

	lock(&procalloc);
	for(;;) {
		if((p =3D procalloc.free) !=3D nil)
			break;

		snprint(msg, sizeof msg, "no procs; %s forking",
			up !=3D nil ? up->text: "kernel");
		unlock(&procalloc);
		resrcwait(msg);
		lock(&procalloc);
	}
	procalloc.free =3D p->qnext;
	unlock(&procalloc);

and rfork(2) says:
	Rfork will sleep, if necessary, until required process resources =
are available.
which is also exists from old day.

Nevertheless all programs, I believe, in /sys/src are written assuming =
rfork() may return -l:
	switch(rfork(=E2=80=A6.)){
	case -1:
	  =E2=80=A6
	}

Any merit?