On Tue, Jul 11, 2017 at 11:42:20AM -0700, Evgeny Baskakov wrote: > 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 > > Jérôme > > 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. >
What are the symptoms ? The program just stop making any progress and you trigger a sysrequest to dump current states of each threads ? In this log i don't see migration_entry_wait() anymore but it seems to be waiting on page lock so there might be 2 issues here. Jérôme
