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From: Hans Petter Selasky <hselasky@c2i.net>
To: freebsd-current@freebsd.org
Subject: Re: double fault [Was: clang compiled kernel panic when mounting zfs
 root on i386]
Date: Sun, 23 Dec 2012 10:41:21 +0100
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Cc: Dimitry Andric <dim@freebsd.org>, Andriy Gapon <avg@freebsd.org>
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On Saturday 22 December 2012 13:59:11 Dimitry Andric wrote:
> On 2012-12-22 12:11, Andriy Gapon wrote:
> > on 21/12/2012 18:38 Hans Petter Selasky said the following:
> >> I've built a 10-current i386 kernel as of today, and I see double fault
> >> when USB audio is allocating memory. Anyone knows why?
> >> 
> >> kdb_enter()
> >> vpanic()
> >> panic()
> >> dblfault_handler()
> >> vm_map_lookup()
> >> vm_fault_hold()
> >> vm_fault()
> >> vm_fault_wire()
> >> vm_map_wire()
> >> kmem_alloc_attr(xxx, 0x4000,2,0,0xffffffff)
> >> bus_dmamem_alloc()
> >> usb_pc_alloc_mem()
> > 
> > I suspect that this double fault may have nothing to do with the thread
> > to which you followed up.
> > 
> > You need to obtain full debug information to answer your question.
> 
> Specifically interesting are the stack frame addresses, which Kostik has
> added recently.  From these, you can easily see whether the double fault
> is due to stack exhaustion (which seems unlikely with such a small call
> stack), or to something else.

Hi,

It was due to running out of stack. I've fixed it in -current.

--HPS