boot hang: async vs. kexec

[Randy Dunlap]

I (try to) do daily build/boot testing.  The newly built kernel
is booted via kexec.  This was working until sometime between
2.6.28 and 2.6.29-rc1, so I bisected it.*

git bisect blames this commit:

96777fe7b042e5a5d0fe5fb861fcd6cd80ef9634 is first bad commit
commit 96777fe7b042e5a5d0fe5fb861fcd6cd80ef9634
Author: Dave Kleikamp <shaggy at linux.vnet.ibm.com>
Date:   Thu Jan 8 09:46:31 2009 -0600

    async: Don't call async_synchronize_full_special() while holding sb_lock
    
    sync_filesystems() shouldn't be calling async_synchronize_full_special
    while holding a spinlock.  The second while loop in that function is the
    right place for this anyway.


The new/kexec-loaded kernel hangs during initcalls.  The last one that
I can see (via netconsole, might miss a few of the very last lines) is:

calling  net_ns_init+0x0/0x14d @ 1
net_namespace: 1008 bytes
initcall net_ns_init+0x0/0x14d returned 0 after 0 usecs



Any ideas/suggestions?
Thanks.



*caveat: This was all done with the "don't use gcc 4.1.[01]
because it miscompiles __weak" patch reverted.  Could that
be an issue/problem here?  (I'm using gcc 4.1.1.)

-- 
~Randy