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From: arisawa <arisawa@ar.aichi-u.ac.jp>
In-Reply-To: <4c37cf728d5b0e7ae4ebd3c2e0c2cee4@brasstown.quanstro.net>
Date: Tue, 27 Jan 2015 09:33:05 +0900
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References: <E9D002A0-CF5A-4059-96F9-9365F67D119B@ar.aichi-u.ac.jp>
	<0F748B67-FB11-464C-84FA-66B4E0B29918@9.offblast.org>
	<44900c0d4896622fa8a9411b05efe730@brasstown.quanstro.net>
	<7A132462-4747-471A-A4BF-D9381E38A4EA@ar.aichi-u.ac.jp>
	<4c37cf728d5b0e7ae4ebd3c2e0c2cee4@brasstown.quanstro.net>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] protection against resource exhaustion
Topicbox-Message-UUID: 3b931f12-ead9-11e9-9d60-3106f5b1d025

Hello,

many of resource exhaustion come from careless programming.
I would like such processes to be killed immediately.
throwing up to broken state might be better.
I prefer an option to plan9.ini that enable resrcwait(), because the =
call breaks
traditional programming style and probably we need more time to have=20
right solution.

> 2015/01/26 23:13=E3=80=81erik quanstrom <quanstro@quanstro.net> =
=E3=81=AE=E3=83=A1=E3=83=BC=E3=83=AB=EF=BC=9A
>=20
> On Mon Jan 26 03:43:36 PST 2015, arisawa@ar.aichi-u.ac.jp wrote:
>> Hello,
>>=20
>> I have been playing the following program.
>> I tried on official plan9, 9front, and 9atom.
>> none of them showed messages that come from:
>> 		sysfatal("fork: %r=E2=80=9D);
>> 		sysfatal("exec: %r");
>> I suspect that
>> 	fork()
>> does not return -1 even if it failed in creating new process.
>=20
> exactly.
>=20
> the reason it never returns -1, is that introduces a new failure case =
in
> every program running, and testing seems like a huge pain.  just
> testing for "handles fork returning -1" is not good enough, it has to =
have
> a reasonable strategy for deailing with no procs.  this is hard to get =
right.
> just reboot.  i have never been able to recover a system that hit =
noprocs.
> i ended up wasting people's time trying.
>=20
> - erik
>=20
> ps.  how may lines like this have you seen.
>=20
> 	p =3D malloc(n);
> 	if(p =3D=3D nil){
> 		...
> 	}
>=20
> is this really useful in most tools?
>=20