code in GEOM thread could not use vnode API (Was: alq_open_flags() panics in _mtx_lock_flags())

[Kostik Belousov]

On Mon, Oct 03, 2011 at 08:27:28PM +0400, Lev Serebryakov wrote:
> Hello, Kostik.
> You wrote 3 октября 2011 г., 20:01:45:
> 
> > Look at the body of e.g. g_io_schedule_down(), the
> >                 THREAD_NO_SLEEPING();
> > call right before the call to geom start method.
> 
> > Basically, you cannot use any kernel subsystem in the context of
> > the up/down threads that could sleep. This includes VFS, VM and
> > everything that is layered on top of it.
>   VM too? Allocating of new element to put into working queue is
>  prohibited? It is what (almost) every GEOM class does.
>   Even geom_nop() allocate new struct bio from g_down thread.
Sleeping (and thus non-failing) allocation is prohibited.
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