Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages_range

[Davidlohr Bueso]

On Tue, 2014-03-11 at 16:45 -0400, Sasha Levin wrote:
> On 03/11/2014 04:30 PM, Andrew Morton wrote:
> > 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?
> >
> > --- a/mm/vmacache.c~a
> > +++ a/mm/vmacache.c
> > @@ -72,8 +72,10 @@ struct vm_area_struct *vmacache_find(str
> >   	for (i = 0; i < VMACACHE_SIZE; i++) {
> >   		struct vm_area_struct *vma = current->vmacache[i];
> >
> > -		if (vma && vma->vm_start <= addr && vma->vm_end > addr)
> > +		if (vma && vma->vm_start <= addr && vma->vm_end > addr) {
> > +			BUG_ON(vma->vm_mm != mm);
> >   			return vma;
> > +		}
> >   	}
> >
> >   	return NULL;
> 
> Bingo! With the above patch:
> 
> [  243.565794] kernel BUG at mm/vmacache.c:76!
> [  243.566720] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [  243.568048] Dumping ftrace buffer:
> [  243.568740]    (ftrace buffer empty)
> [  243.569481] Modules linked in:
> [  243.570203] CPU: 10 PID: 10073 Comm: trinity-c332 Tainted: G        W    3.14.0-rc5-next-20140307-sasha-00010-g1f812cb-dirty #143

and this is also part of the DEBUG_PAGEALLOC + trinity combo! I suspect
the root cause it the same as Fengguang's report.

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