From: Ingo Molnar <redacted>
Date: Thu, 15 Apr 2010 08:49:40 +0200

Btw., WARN_ON trapping on PowerPC is clearly a PowerPC bug - there's a good 
reason we have WARN_ON versus BUG_ON - it should be fixed.

I disagree, an implementation should be allowed to use the most
efficient implementation possible for both interfaces.

I would be using traps for both on sparc64 if that were really
feasible on sparc64 (and actually with gcc-4.5's "asm goto" it might
actually be now)

The WARN and BUG macros, when implemented without traps, have serious
implications for overall code size and register pressure.