Messages in this thread | | | Date | Fri, 22 Feb 2013 09:54:38 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] nohz: Make tick_nohz_irq_exit() irq safe |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Thu, Feb 21, 2013 at 10:21 AM, Thomas Gleixner <tglx@linutronix.de> wrote: > > > > This was a draft patch. I made it a WARN_ON_ONCE() already. > > Ok, good. > > I really wish we could just get rid of BUG_ON(). It was a bad > idea, and it makes it easy for people to do the wrong thing. > Sadly, we have tons of them.
So my old plan was to use a little bit of psychology.
Firstly, we could just turn BUG_ON() into a WARN() variant that emits:
BUG: ...
while a WARN()ings emit:
WARNING: ...
and then we could introduce a new primitive:
CRASH_ON();
which would be used in the (few) places that really, really cannot continue sanely and need to crash the box.
This naming alone would inhibit its use through two channels:
- Putting the word 'CRASH' into your code feels risky, dissonant and wrong (perfect code does not crash) and thus needs conscious frontal lobe effort to justify it - while BUG_ON() really feels more like a harmless assert to most kernel developers, which is in our muscle memory through years training.
- CRASH_ON() takes one character more typing than WARN_ON(), and we know good kernel developers are fundamentally lazy.
[ This is an arguably lazy plan that does not involve changing the 10,000+ BUG_ON() call sites and does not involve the re-training of thousands of mis-trained kernel developers who introduced over 900 new BUG_ON()s in the v3.7->v3.8 cycle alone (!). ]
So while I don't think we can win the war against BUG_ON(), I think we can fight the lazy general's war: turn the enemy over to our side and declare victory?
Thanks,
Ingo
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