Date: Wed, 12 Dec 2012 14:38:23 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Alfred Perlstein <alfred@freebsd.org>, src-committers@freebsd.org, John Baldwin <jhb@freebsd.org> Subject: Re: svn commit: r244112 - head/sys/kern Message-ID: <CAJ-Vmo=sP0uojVBM9MdY7jL%2BUZoN5mj%2Bim_MBdq9U%2B8uRuTv3A@mail.gmail.com> In-Reply-To: <50C90567.8080406@FreeBSD.org> References: <201212110708.qBB78EWx025288@svn.freebsd.org> <201212121046.43706.jhb@freebsd.org> <CAJ-Vmo=U04GX%2BZyKuzXLwV%2BPpzU6_dm5BCmL=DWfsmhTVAR%2BsA@mail.gmail.com> <201212121658.49048.jhb@freebsd.org> <50C90567.8080406@FreeBSD.org>
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There are two parts to this; * don't compile in invariants. Panics panic. Invariant conditions aren't checked. You end up with data corruption still if there are bugs. * compile in invariants. Panics panic. Invariant conditions are checked and immediately panic. You can't run this in production to get debugging info because our debugging info is "create a crash dump and reboot." Now, the crash dump is great for us developers. But crap for say, a file server. If it's some very subtle issue that only occasionally pops up once a week and doesn't obviously screw with your data: * you can enable invariants and get a crash dump each time - then us developers get lots of information, but the user experiences outages once a week; * they just give the hell up, disable invariants in production and occasionally hit odd issues they can't explain. So now there's a third option: * enable invariants, get told when you hit that condition, and continue running. Now, we ship _right now_ generic with INVARIANTS disabled, because in theory the releases are supposed to be stable enough for us not to need the extra debugging information. That means that for those very occasional, very subtle bugs that invariants may catch, we don't have any way of getting told about them. Now, enabling some alternative to panic() is a different story and not what's being addressed here. HTH, Adrian
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