On 7/11/17 11:29 AM, Jerome Glisse wrote:
> Can you test if attached patch helps ? I am having trouble reproducing 
> this
> from inside a vm.
>
> My theory is that 2 concurrent CPU page fault happens. First one manage to
> start the migration back to system memory but second one see the migration
> special entry and call migration_entry_wait() which increase page refcount
> and this happen before first one check page refcount are ok for migration.
>
> For regular migration such scenario is ok as the migration bails out and
> because page is CPU accessible there is no need to kick again the migration
> for other thread that CPU fault to migrate.
>
> I am looking into how i can change migration_entry_wait() not to refcount
> pages. Let me know if the attached patch helps.
>
> Thank you
> Jerome

Hi Jerome,

Thanks for the update.

Unfortunately, the patch does not help. I just applied it and recompiled 
the kernel. Please find attached a new kernel log and an app log.

-- 
Evgeny Baskakov
NVIDIA