Date: Thu, 13 Dec 2012 00:37:30 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Adrian Chadd <adrian@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: <50C9072A.6040605@FreeBSD.org> In-Reply-To: <CAJ-Vmo=U04GX%2BZyKuzXLwV%2BPpzU6_dm5BCmL=DWfsmhTVAR%2BsA@mail.gmail.com> References: <201212110708.qBB78EWx025288@svn.freebsd.org> <201212121046.43706.jhb@freebsd.org> <CAJ-Vmo=U04GX%2BZyKuzXLwV%2BPpzU6_dm5BCmL=DWfsmhTVAR%2BsA@mail.gmail.com>
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on 12/12/2012 19:06 Adrian Chadd said the following: > kassert()s are already optional. Ie, you can choose to not compile them in. > > So the __dead2() code path bit for doing KASSERT() -> kassert_panic() > at compile time isn't a problem. > > The problem is where you do panic() -> kassert_panic() (eg in the > Witness code) which is what Alfred discovered shortly after doing up > his initial patch. > > Anything which is a KASSERT() can and should be treated as a run-time > warning just as much as a run-time "crash here so I can figure out > what broke." Having the warning in a production box is going to be > helpful for developers. I have a quite different view on purpose and costs of KASSERTs. Specifically referring to r243980 I do not think that "non-fatal asserts" should really exist (or do exist). I wish all this muddying of KASSERT meaning would get reverted. These quite sensitive changes were rushed in, IMO. > On 12 December 2012 07:46, John Baldwin <jhb@freebsd.org> wrote: >> On Tuesday, December 11, 2012 2:08:14 am Alfred Perlstein wrote: >>> Author: alfred >>> Date: Tue Dec 11 07:08:14 2012 >>> New Revision: 244112 >>> URL: http://svnweb.freebsd.org/changeset/base/244112 >>> >>> Log: >>> Cleanup more of the kassert_panic. >>> >>> fix compile warnings on !amd64 and NULL derefs that would happen >>> if kassert_panic() would return. >> >> This is one reason why having kassert not panic is such a bad idea. There are >> tons of places where the compiler knows that panic() is __dead2, and there is >> no cleanup code to handle what happens when an invariant is violated. This is >> not safe to run in the field unless your customers do not care about their >> data. If you are interested in doing regression tests, I am using a very >> different approach for some locking regression tests I am working on in p4 >> that allow you to use a wrapper around setjmp/longjmp to "catch" panics >> somewhat like exception handling in C++/Java (though much cruder). However, >> evne that is only intended for testing, not for production cases where >> production data is at stake. >> >> -- >> John Baldwin -- Andriy Gapon -- Andriy Gapon
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