From owner-freebsd-stable@freebsd.org  Fri Sep 16 10:17:18 2016
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Date: Fri, 16 Sep 2016 13:17:14 +0300
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: John Baldwin <jhb@freebsd.org>, freebsd-stable@freebsd.org
Subject: Re: nginx and FreeBSD11
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On Fri, Sep 16, 2016 at 12:16:17PM +0300, Konstantin Belousov wrote:

> 
> vmspace_switch_aio() allows context switching with old curpmap
> and new proc->p_vmspace. This is a weird condition, where
> curproc->p_vmspace->vm_pmap is not equal to curcpu->pc_curpmap. I do
> not see an obvious place which would immediately break, e.g. even
> for context switch between assignment of newvm to p_vmspace and
> pmap_activate(), the context-switch call to pmap_activate_sw() seems to
> do right thing.
> 
> Still, just in case, try this
> 
> diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
> index a23468e..fbaa6c1 100644
> --- a/sys/vm/vm_map.c
> +++ b/sys/vm/vm_map.c
> @@ -481,6 +481,7 @@ vmspace_switch_aio(struct vmspace *newvm)
>  	if (oldvm == newvm)
>  		return;
>  
> +	critical_enter();
>  	/*
>  	 * Point to the new address space and refer to it.
>  	 */
> @@ -489,6 +490,7 @@ vmspace_switch_aio(struct vmspace *newvm)
>  
>  	/* Activate the new mapping. */
>  	pmap_activate(curthread);
> +	critical_exit();
>  
>  	/* Remove the daemon's reference to the old address space. */
>  	KASSERT(oldvm->vm_refcnt > 1,

OK, nginx core dumped, kernel don't crushed.
Now I am try this patch (critical_enter) and reboot.

PS: vi regresion: can't exit from vi when no space on /tmp