Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages_range

[Sasha Levin]

On 03/11/2014 04:30 PM, Andrew Morton wrote:
> 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.

That's actually seems right because if 'ret & VM_FAULT_RETRY' is true it means that
lock_page_or_retry() was supposed to release mmap_sem for us.


Thanks,
Sasha
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