Re: [REPOST PATCH 1/8] fence: dma-buf cross-device synchronization (v17)

On Thu, Jun 19, 2014 at 7:00 PM, Greg KH [off-list ref] wrote:

quoted

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+     BUG_ON(f1->context != f2->context);

Nice, you just crashed the kernel, making it impossible to debug or
recover :(

agreed, that should probably be 'if (WARN_ON(...)) return NULL;'

(but at least I wouldn't expect to hit that under console_lock so you
should at least see the last N lines of the backtrace on the screen
;-))

Lots of devices don't have console screens :)

Aside: This is a pet peeve of mine and recently I've switched to
rejecting all patch that have a BUG_ON, period. Except when you can
prove that the kernel will die in the next few lines and there's
nothing you can do about it a WARN_ON is always better - I've wasted
_way_ too much time debugging hard hangs because such a "benign"
BUG_ON ended up eating my irq handler or a spinlock required by such.
Or some other nonsense that makes debugging a royal pita, especially
if your remote debugger consists of a frustrated users staring at a
hung machine.

</rant>

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch