Re: Fatal Oops on boot with 2.4.0testX and recent GCC snapshots

[Andreas Franck <afranck@gmx.de>]

Hello Mike, hello linux-kernel hackers,

Mike Galbraith wrote:

> Yes, hmm indeed.  Try these two things.
> 
> 1. make DECLARE_MUTEX_LOCKED(sem) in bdflush_init() static.
> 2. compile with frame pointers.  (normal case for IKD)
> 
> My IKD tree works with either option, but not with neither.  I haven't
> figured out why yet.

1 worked for me, too - with the same effect as compiling buffer.c with 
2.95.2, thus meaning successful boot and heavy crashing later on. 
I haven't tried to boot 2 yet, but this looks seriously fishy to me. It would 
be nice if we could make a simpler testcase to reproduce it, as it's much 
work to boot the kernel over and over again.

I have now printed out the buffer.c:bdflush_init assembly for all four cases, 
2.95.2, 2.97 without patch, 2.97 with static DECLARE... and 2.97 with frame 
pointer, and will try to figure out what's going wrong - it would still be 
nice to know if its a gcc problem or if some kernel assumption about GCC 
behaviour triggered this bug, which seems equally likely, as kernel_thread 
and the mutex/semaphore stuff involve some nontrivial (at least for beginners 
like me...) hand-made assembly code.

A nice evening and still merry christmas to the people westward of Europe :-)

Andreas

-- 
->>>----------------------- Andreas Franck --------<<<-
---<<<---- Andreas.Franck@post.rwth-aachen.de --->>>---
->>>---- Keep smiling! ----------------------------<<<-
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