Re: [RFC PATCH 0/2] avoid clobbering registers with J_ASSERT macro

[Chris Snook <csnook@redhat.com>]

Andrew Morton wrote:
> On Fri, 17 Aug 2007 01:54:18 -0400
> Chris Snook <csnook@redhat.com> wrote:
> 
>> The J_ASSERT() macro in jbd and jbd2 calls printk() prior to BUG().  While this 
>> makes it more convenient to read the assertion failure, it also clobbers 
>> registers, which can sometimes make debugging harder, which is clearly not the 
>> intended purpose.  I recently banged my head on this myself.
>>
>> The following patches to jbd and jbd2 enable the printk only if 
>> CONFIG_JBD[2]_DEBUG is set.  Otherwise, it will simply BUG if the condition is 
>> violated.  This way test kernels still get the benefit of the J_ASSERT printk, 
>> while production kernels, which come from a more stable source base where it's 
>> easier to trace line numbers back to specific lines of code, simply get the BUG, 
>> with all registers preserved.
>>
>> This is, of course, not the only way of fixing this problem, but it seems to be 
>> the least invasive way, which is why I'm proposing these patches.
> 
> How's about we just remove that printk?  Do
> 
> #define J_ASSERT(e) BUG_ON(e)?
> 
> The rest of the kernel seems to be able to cope with that...

Perfectly fine with me.  I proposed the conditional on the grounds that someone 
probably had a purpose for the original J_ASSERT macro at some point in history, 
but if that purpose is long since obsolete, let's just get rid of it.  I'll repost.

	-- Chris