Re: [linux-usb-devel] OOM and USB, latest Linux 2.6

[Dan Aloni]

Dan Aloni wrote:
> Alan Stern wrote:
[...]
> > Can you be any more specific than that?  usb-storage should use only 
> > GFP_NOIO in its I/O paths.
> >
> >
> >   
> You are right, I looked over this state with kdb, and usb-storage
> waited in usb_stor_bulk_transfer_sg, which does pass GFP_NOIO
> at this scenario.
>
> It looked suspicious though, because OOM handling was invoked
> from many processes, and it didn't print about any process being
> killed and it didn't complain about no processes to kill either.
Hmm, I'm pretty sure I stomped over this (from select_bad_process()):

               /*
                * This task already has access to memory reserves and is
                * being killed. Don't allow any other task access to the
                * memory reserve.
                *
                * Note: this may have a chance of deadlock if it gets
                * blocked waiting for another task which itself is waiting
                * for memory. Is there a better alternative?
                */
               if (test_tsk_thread_flag(p, TIF_MEMDIE))
                       return ERR_PTR(-1UL);

Which might explains why the OOM handling was behaving like it did.

It would have been nice if it at least printed "OOM: I'm in a deadlock,
please FIXME...".

--
Dan Aloni
XIV LTD, http://www.xivstorage.com
da-x (at) monatomic.org, dan (at) xiv.co.il

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