On 03/04/2014 10:16 PM, Bob Liu wrote:
On Thu, Feb 27, 2014 at 11:03 PM, Kirill A. Shutemov
<[email protected]> wrote:
Sasha Levin wrote:
Hi all,

While fuzzing with trinity inside a KVM tools guest running latest -next kernel 
I've stumbled on the
following spew:

[ 1428.146261] kernel BUG at mm/huge_memory.c:2785!

Hm, interesting.

It seems we either failed to split huge page on vma split or it
materialized from under us. I don't see how it can happen:

   - it seems we do the right thing with vma_adjust_trans_huge() in
     __split_vma();
   - we hold ->mmap_sem all the way from vm_munmap(). At least I don't see
     a place where we could drop it;


Enable CONFIG_DEBUG_VM may show some useful information, at least we
can confirm weather rwsem_is_locked(&tlb->mm->mmap_sem) before
split_huge_page_pmd().

I have CONFIG_DEBUG_VM enabled and that code you're talking is not triggering, 
so mmap_sem
is locked.


Thanks,
Sasha
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