Re: 2.5.70 (virgin) hangs running SDET

[Andrew Morton]

"Martin J. Bligh" <[e-mail]> wrote:
>
> I thought this was specific to the -mjb tree for a while, but I can
> reproduce it pretty easily on virgin 2.5.70 (but 2.5.69 didn't do
> this). Andrew looked and pointed out it seems to be an i_sem (ISTR
> some mention of /proc somewhere too?). Got a good sysrq+t trace out
> of the virgin kernel (on 16x NUMA-Q) ... below:

The ps instance which is spinning on kernel_flag in proc_root_lookup is
what's holding things up.

Or is it spinning in proc_lookup() or proc_pid_lookup()?  I have a vague
feeling that I've seen these traces miss out the innermost stack slot...

Suggest:

a) Use CONFIG_SPINLINE, get a new sysrq-T trace

b) Enable spinlock debugging

c) Try disabling the sched_balance_exec() code.