Re: bugs with ckpt-v15-dev

[Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>]

"Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> writes:

> Quoting Nathan Lynch (ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org):
>> "Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> writes:
>> 
>> > Quoting Nathan Lynch (ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org):
>> >> Last commit is ed3b275 "allow error string during checkpoint while
>> >> holding a spinlock".
>> >> 
>> >> # bash -c 'exec <&- >&- 2>&- ; while : ; do : ; done' &
>> >> [1] 2269
>> >> # ckpt $! > /tmp/bash.ckpt
>> >> 
>> >> BUG: sleeping function called from invalid context at mm/slub.c:1595
>> >
>> > Yeah, not only does ckpt_write_err() get called under task_lock, but
>> > the fn returns without ver doing put_task_struct.  (I'd generate and
>> > send the quick trivial patch, but my git tree is in a bit of a debugme
>> > state right now)
>> 
>> Would prefer to just rip that thing out, it's cost me more trouble then
>> it's worth.
>
> Which thing - CHECKPOINT_SUBTREE, freezer check, or ckpt_write_err?

ckpt_write_err.  I've yet to witness it perform its intended function
without triggering a WARN_ON or BUG.


>> > Now mind you this shows that your ckpt program isn't sending
>> > CHECKPOINT_SUBTREE with flags.
>> 
>> I don't follow.  There is "user error" here in that I'm not freezing the
>> task before checkpointing[1], but my ckpt command is passing the subtree
>> flag (0x4) afaict:
>> 
>> SYS_335(0x9ec, 0x1, 0x4, 0xbfdc6200, 0[2542:c/r:may_checkpoint_task] check 2540
>
> Oh, it's the freezer test in may_checkpoint_task you're getting the
> error on?  (in my git tree I'd commented that one out temporarily so I
> just assumed it was the subtree check in get_container :)

Yes, the frozen test is failing, afaik.