Re: [BUG -rt] Double OOPs - thread_info free race / printk recursive lock

From: hui
Date: Fri Aug 04 2006 - 17:08:05 EST

On Fri, Aug 04, 2006 at 10:43:05AM -0700, Darren Hart wrote:
> We've seen very rarely over the last few months, on various -rt kernels. The
> latest reproduction is on 2.6.16-rt22 (+some minor fixups). Analysis of the
> vmcore produced by kdump suggests two problems:
> 1) An invalid pointer dereference in cache_flusharray() which causes the page
> fault.

My guess is that this is after some bogus stuff going on after the real event.

> 2) Then printk calls kmalloc when trying to print the oops, which grabs a
> recursive lock and prints a different oops.

Can't say for sure, but this sounds a lot like the problem I've been dealing
with in free_task(). The stack trace is pretty contorted and it's been difficult
to unwind it in any meaningful manner, although I'm making progress. Writing
some tools to deal with this now.


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