Date: Thu, 25 Sep 2014 12:21:03 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Davide Italiano <davide@freebsd.org> Cc: Adrian Chadd <adrian@freebsd.org>, "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org>, Bryan Drewery <bdrewery@freebsd.org> Subject: Re: KASSERT_WARN for asserting malloc(M_WAITOK) not in a non-sleepable thread Message-ID: <1411669263.66615.249.camel@revolution.hippie.lan> In-Reply-To: <CACYV=-HDVxhQ=CDK7HWuK2t-rsFkW2gKD45NDjC86jQ2wq6v9A@mail.gmail.com> References: <54236CD6.4050807@FreeBSD.org> <CACYV=-Eg69AQ72DOGppPSL7whJVCdcNg-auhBZ771iG7DfPdAw@mail.gmail.com> <5424392D.9030201@FreeBSD.org> <CAJ-Vmok5Xaa6aZvfL1GoW8C==dY47P=vKAEZhu16JhHjV%2BTk9g@mail.gmail.com> <CACYV=-GMpMxEAs-X7umMdYX2Awf3G0La1cUGsXeH9MoX34CdxQ@mail.gmail.com> <1411668571.66615.247.camel@revolution.hippie.lan> <CACYV=-HDVxhQ=CDK7HWuK2t-rsFkW2gKD45NDjC86jQ2wq6v9A@mail.gmail.com>
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On Thu, 2014-09-25 at 11:16 -0700, Davide Italiano wrote: > On Thu, Sep 25, 2014 at 11:09 AM, Ian Lepore <ian@freebsd.org> wrote: > > On Thu, 2014-09-25 at 10:51 -0700, Davide Italiano wrote: > >> On Thu, Sep 25, 2014 at 9:14 AM, Adrian Chadd <adrian@freebsd.org> wrote: > >> > Hi, > >> > > >> > Please bring in KASSERT_WARN(). > >> > > >> > I'm grown up enough to use KASSERT_WARN() along with handling the > >> > invariant check myself in code. Having KASSERT_WARN() means I can add > >> > in this rather than printf()s or device_printf()'s with various knobs > >> > to remove it. > >> > > >> > (This is absolutely _not_ the "should KASSERT() optionally just log" > >> > argument. I'm not going to get into that a second time.) > >> > > >> > > >> > >> If you put a KASSERT() inside your code -- probably you should be > >> careful enough to put that iff you're sure that it should be always > >> verified. No exceptions. > >> People tend to be very lazy (including me). I don't expect everybody > >> diligently upgrading KASSERT_WARN to KASSERT. So KASSERT_WARN start > >> becoming more and more widespread, and people realize all of these > >> need to be upgraded to KASSERT or removed. This generally happens > >> after years. Yet. Another. Crusade. > >> There's a lot of work in the kernel to remove old/wrong/naive KPI > >> from the kernel. jhb@ is looking at timeout()-> callout() conversion. > >> I'm personally looking at dev_clone() removal. There are a lot of > >> other examples. > >> Adding KASSERT_WARN is a step backward, not a step forward, IMHO. > >> That said, if you want to pollute the kernel, fine. I expressed my > >> opinion, and I'm personally not happy about this, but I never stated > >> I'm gonna stop you from doing that. > >> > >> Thanks, > >> > >> -- > > > > IMO, this entire argument is ridiculous. Some conditions are so insane > > that you've got to stop immediately rather than make things worse. > > Other conditions indicate problems, but the code can recover or > > otherwise continue to operate safely. Trying to define every possible > > anomalous condition as either fatal or not worth mentioning is insane. > > > > Everyone is free to write code such as > > > > #ifdef INVARIANTS > > if (some_condition) > > printf("whatever warning\n"); > > #endif > > > > So let's be clear here: the objections are to spelling that code > > sequence KASSERT_WARN. If you object, please explain what's wrong with > > that spelling and how you would prefer it to be spelled. > > > > -- Ian > > > > > > Take the assert out of the name. Call it DEBUG_WARN, or something else > if you like. > assert as a pretty *clear* and specific semantic, no need to mess > around with it. > > Thanks, > To me, another "clear and specific semantic" that's associated with the word 'assert' in C programming is that the test expression itself is automatically printed as part of the diagnostic message. That's not the case in the FreeBSD kernel, so I guess we need to rename KASSERT as well? -- Ian
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