On 02/21/2014 08:37 PM, Sebastian Capella wrote: > Quoting Sebastian Capella (2014-02-21 15:59:11) >> - Cyril Chemparathy as his email is bouncing back to me. >> >> Quoting Sebastian Capella (2014-02-21 10:39:56) >>> Quoting Lorenzo Pieralisi (2014-02-20 08:27:55) >>>>>>> + cpu_switch_mm(idmap_pgd, &init_mm); >> [ ... ] >>> I can try removing it and seeing if there are side effects. >> >> FYI, It's definitely hanging with this removed, still looking. > > I see when we reach this call, the 1st level page table @ TTBR0 is located > at different memory locations each run (expected). If we omit the > cpu_switch_mm we're corrupting the page table causing the observed > intermittent failures. I believe these match the corruption you expected. > > The reason this doesn't happen when I leave the call is that idmap_pgd > is always at the same memory location. I expect this is because it's > allocated during init. I've seen the same address 50/50 times for > idmap_pgd. I don't think it is correct to rely on this behavior. > > Would it be appropriate to use the swapper_pg_dir directly in place > of idmap_pgd? > - I do not see any modification to the swapper_pg_dir contents in the > code that would change from init time. > - swapper_pg_dir is always at the same offset. > > Ideally we should have no issue with overwriting it with identical data. > > I've run a couple hundred test loops using swapper_pg_dir and so far > there are no failures.
If there is worry about this, you could setup a page mapping in a __nosave region, preventing it from being overwritten. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
