Re: allocating memory during kernel startup

[Michael <macallan%netbsd.org@localhost>]

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Hello,

On May 6, 2010, at 10:19 PM, Masao Uebayashi wrote:

> On Thu, May 06, 2010 at 02:32:57PM -0400, Michael wrote:
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> > Hello,
> >
> > I recently ran into this problem - there is no easy way to determine
> > wether it is safe to call kmem_alloc() yet ( as in, are we far
> > enough through startup ) and when we call it too early the whole
> > thing just hangs.
>
> We have no clear definition of the kernel state - what is boot,  
> startup,
> and when it's done.

Yeah, we only have cold and that's not what I need.

> > Any chance to just have kmem_alloc() immediately return NULL if it
> > isn't ready yet so we can fail gracefully instead of hanging?
>
> I like panic().
>
> I think that complicating memory allocation in bootstrap is not a good
> thing.  What is your purpose?

It's rasops_reconfig(). It may want to autogenerate box drawing  
characters, which needs to allocate memory, but it can happily live  
without them and some ports ( macppc for example ) setup a rasops- 
based console very early in the boot process. In this case  
rasops_reconfig() should simply skip the character generating process  
instead of something nasty like a panic to happen.
Also, the man page suggests that kmem_alloc(KM_NOSLEEP) would return  
NULL if memory can't be allocated which would be the case.

have fun
Michael

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