On Tue, 2014-03-11 at 13:30 -0700, Andrew Morton wrote: > On Tue, 11 Mar 2014 13:07:33 -0700 Davidlohr Bueso <davidl...@hp.com> wrote: > > > On Tue, 2014-03-11 at 15:39 -0400, Sasha Levin wrote: > > > Hi all, > > > > > > I've ended up deleting the log file by mistake, but this bug does seem to > > > be important > > > so I'd rather not wait before the same issue is triggered again. > > > > > > The call chain is: > > > > > > mlock (mm/mlock.c:745) > > > __mm_populate (mm/mlock.c:700) > > > __mlock_vma_pages_range (mm/mlock.c:229) > > > VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); > > > > So __mm_populate() is only called by mlock(2) and this VM_BUG_ON seems > > wrong as we call it without the lock held: > > > > up_write(¤t->mm->mmap_sem); > > if (!error) > > error = __mm_populate(start, len, 0); > > return error; > > } > > __mm_populate() pretty clearly calls __mlock_vma_pages_range() under > down_read(mm->mmap_sem). > > I worry about what happens if __get_user_pages decides to do > > if (ret & VM_FAULT_RETRY) { > if (nonblocking) > *nonblocking = 0; > return i; > } > > uh-oh, that just cleared __mm_populate()'s `locked' variable and we'll > forget to undo mmap_sem. That won't explain this result, but it's a > potential problem. > > > All I can think is that find_vma() went and returned a vma from a > different mm, which would be odd. How about I toss this in there?
... and we know that there is a bug (https://lkml.org/lkml/2014/3/9/201) with stale caches going on. We seem to be missing an invalidation and/or flush somewhere. -- 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/