linux-kernel - Re: Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c

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Date:	Fri, 22 Aug 2008 11:37:33 -0400
From:	"Alan D. Brunelle" <Alan.Brunelle@...com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected

Andrew Morton wrote:

> 
> You could confirm/debug it with something along the lines of this:
> 
> --- a/mm/vmalloc.c~a
> +++ a/mm/vmalloc.c
> @@ -214,7 +214,9 @@ __get_vm_area_node(unsigned long size, u
>  	unsigned long align = 1;
>  	unsigned long addr;
>  
> -	BUG_ON(in_interrupt());
> +	if (preempt_count() > 10)
> +		printk("%s: preempt_count()=%d\n", __func__, preempt_count());
> +	WARN_ON(in_interrupt());
>  	if (flags & VM_IOREMAP) {
>  		int bit = fls(size);
>  
> _
> 
> 
> But this bug could be in practically anywhere in the kernel and
> bisection is by far the best way to find it.  It's sad and odd that
> bisection landed you on a merge commit.  I'd suggest that you persist
> with the bisection (please). 
> http://www.kernel.org/doc/local/git-quick.html#example might be useful.

Sorry, was off on other things for the last couple of days:

I /did/ bisect it down to the aforementioned merge, the question is: How
to crack open that merge into it's composite pieces? (Where do I go to
bisect within that?)

I'll try the patch above, and see what that reports.

Alan
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