Re: [RFC v3 05/17] RCU free VMAs

[Laurent Dufour]

On 30/04/2017 07:05, Matthew Wilcox wrote:
> On Thu, Apr 27, 2017 at 05:52:44PM +0200, Laurent Dufour wrote:
>> +static inline bool vma_is_dead(struct vm_area_struct *vma, unsigned int sequence)
>> +{
>> +	int ret = RB_EMPTY_NODE(&vma->vm_rb);
>> +	unsigned seq = ACCESS_ONCE(vma->vm_sequence.sequence);
>> +
>> +	/*
>> +	 * Matches both the wmb in write_seqlock_{begin,end}() and
>> +	 * the wmb in vma_rb_erase().
>> +	 */
>> +	smp_rmb();
>> +
>> +	return ret || seq != sequence;
>> +}
> 
> Hang on, this isn't vma_is_dead().  This is vma_has_changed() (possibly
> from live to dead, but also possibly grown or shrunk; see your earlier
> patch).

This makes sense.

Thanks,
Laurent