Re: [PATCH] mm,hwpoison: non-current task should be checked early_kill for force_early

["HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>]

On Mon, Jan 18, 2021 at 05:09:00PM +0800, Aili Yao wrote:
> On Mon, 18 Jan 2021 08:57:47 +0000
> HORIGUCHI NAOYA(堀口　直也) <naoya.horiguchi@nec.com> wrote:
> 
> > > > 
> > > > For action optional cases, one error event kills *only one* process. If an
> > > > error page are shared by multiple processes, these processes will be killed
> > > > by separate error events, each of which is triggered when each process tries
> > > > to access the error memory.  So these processes would be killed immediately
> > > > when accessing the error, but you don't have to kill all at the same time
> > > > (or actually you might not even have to kill it at all if the process exits
> > > > finally without accessing the error later).
> > > > 
> > > > Maybe the function variable "force_early" is named confusingly (it sounds
> > > > that it's related to PF_MCE_KILL_EARLY flag, but that's incorrect).
> > > > I'll submit a fix later.  (I'll add your "Reported-by" because you made me
> > > > find it, thank you.)
> > > >   
> > > I think we should do more for non current process error case, we should mark it AO for processes to be signaled
> > > or we may take wrong action.  
> > 
> > I'm not sure what you mean by "non current process error case" and "we
> > should mark it AO", so could you explain more specifically about your error
> > scenario?  
>   I will share my test code and i will submit another patch to this scenario.
>   please give me some time, thanks!
>   And I think you are right, AR is only current process.
> 
> > Especially I'd like to know about who triggers hard offline on
> > what hardware events and what "wrong action" could happen.  Maybe just
> > "calling memory_failure() with MF_ACTION_REQUIRED" is not enough, because
> > it's not enough for us to see that your scenario is possible. Current
> > implementation implicitly assumes some hardware behavior, and does not work
> > for the case which never happens under the assumption.
> > 
>   This action is from mcelog daemon, normally softpage offlie is default, but we can configure
> hardpage offline for CE storms, to get related processes signaled.

Thanks, so which interface did you use for error injection? I guess first
you used /sys/devices/system/memory/hard_offline_page, but if it's true,
then the error event should be action optional (no MF_ACTION_REQUIRED set).
So now I'm wondering why you are observing action required events?
My another guess is that you might have used mce-inject tool, if that's true,
please use hard_offline_page, then current kernel code should properly send
SIGBUS to dedicated process.

- Naoya