Messages in this thread | | | Date | Thu, 21 Dec 2006 10:49:01 -0800 | From | Jeremy Fitzhardinge <> | Subject | Re: [patch] change WARN_ON back to "BUG: at ..." |
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Ingo Molnar wrote: > Subject: [patch] change WARN_ON back to "BUG: at ..." > From: Ingo Molnar <mingo@elte.hu> > > WARN_ON() ever triggering is a kernel bug. Do not try to paper over this > fact by suggesting to the user that this is 'only' a warning, as the > following recent commit does: > I disagree.
I think there are two issues here: intent and effect.
What's the intent of WARN_ON? Presumably its different from BUG_ON, otherwise you could just use BUG_ON. Or if not, why not just have BUG_ON? I think in practice many WARN_ONs are clearly not intended to be as serious as BUG_ON: they warn about unimplemented things, transient hiccups, clarifications of errno returns, etc. (Whether WARN_ON is a good mechanism for all these things is a separate issue.)
Their effects are very different too. The effect of WARN_ON is simply a message; if I see it in a log, I know that something happened which should be fixed, but the system is in a fairly sane state. If I see a BUG_ON, then I know something was killed with extreme prejudice - at best a process got killed, but there may be stray locks held or other damage - and the system is basically teetering if it hasn't crashed already. Because the effects of the two warning mechanisms are so different, I think its important to make them clearly visually distinct when scanning the kernel output. My eye is trained to see "BUG: " as meaning "something destabilizing happened"; if warnings also appear that way, then it is just needlessly confusing.
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