Re: 2.6.0-test7-mm1

[Andrew Morton <akpm@osdl.org>]

Ben Collins <bcollins@debian.org> wrote:
>
> > highlevel_add_host() does read_lock() and then proceeds to do things like
>  > starting kernel threads under that lock.  The locking is pretty broken
>  > in there :(
> 
>  No, highlevel_add_host() itself doesn't start any threads. But it does
>  pass around data that needs to be locked from changes, and one of the
>  handlers happens to start a thread, and other things allocate memory
>  (such as this case).
> 
>  It's ugly, and I've been trying to clean it up. This case can be fixed
>  quickly with a simple check in hpsb_create_hostinfo() to pass GFP_ATOMIC
>  to kmalloc.

nodemgr_add_host() looks like the hard one.  Maybe make hl_drivers_lock a
sleeping lock?

>  My problem right now, is I don't use any architectures that support
>  preempt, so I don't see a lot of these problems, like I catch with
>  CONFIG_SMP.

Anton had a ppc64 patch which implemented the preempt_count beancounting
without actually implementing premption.  So might_sleep() does the right
thing.