9-STABLE panic on intensive fork

[Konstantin Belousov]

On Wed, Aug 28, 2013 at 06:20:29PM +0400, Dmitry Sivachenko wrote:
> Hello!
> 
> I am using very recent FreeBSD-9-STABLE snapshot:
> 9.2-PRERELEASE FreeBSD 9.2-PRERELEASE #0 r254986: Wed Aug 28 17:18:57 MSK 2013
> 
> I run uwsgi program (ports/www/uwsgi) on that machine.
> 
> When uwsgi starts, it forks pre-configured number of worker processes.
> If I raise workers parameter high enough (128), I get kernel panic (100% reproducible):
> 
> Fatal trap 12: page fault while in kernel mode
> 
> If I compile kernel with KDB enabled, I get the following stack:
> 
> pmap_demote_pde_locked()
> pmap_copy()
> vmspace_fork()
> fork1()
> sys_fork()
> 
> I have only remote console for that machine, so I made 2 screenshots:
> 
> 1) http://people.freebsd.org/~demon/screen1.jpg
> Panic screen when kernel has no KDB support compiled in
> 
> 2) http://people.freebsd.org/~demon/screen2.jpg
> Panic screen (2nd part) with the above stack shown.
Look up the source line for the pmap_demote_pde_locked()+0x471 for your
kernel.  Dump the core from the panic.
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