On 3/9/20 4:19 PM, Oleksandr Natalenko wrote: > On Mon, Mar 09, 2020 at 04:08:15PM +0100, Michal Hocko wrote: >> On Mon 09-03-20 14:11:17, Oleksandr Natalenko wrote: >> > On Fri, Mar 06, 2020 at 05:08:18PM +0100, Vlastimil Babka wrote: >> [...] >> > > Dunno, it's nice to react to signals quickly, for any proces that gets them, no? >> > >> > So, do you mean something like this? >> > >> > === >> > diff --git a/mm/ksm.c b/mm/ksm.c >> > index 363ec8189561..b39c237cfcf4 100644 >> > --- a/mm/ksm.c >> > +++ b/mm/ksm.c >> > @@ -849,7 +849,8 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma, >> > for (addr = start; addr < end && !err; addr += PAGE_SIZE) { >> > if (ksm_test_exit(vma->vm_mm)) >> > break; >> > - if (signal_pending(current)) >> > + if (signal_pending(current) || >> > + signal_pending(rcu_dereference(vma->vm_mm->owner))) >> > err = -ERESTARTSYS; >> > else >> > err = break_ksm(vma, addr); >> > === >> >> This is broken because mm might be attached to different tasks. >> AFAIU this check is meant to allow quick backoff of the _calling_ >> process so that it doesn't waste time when the context is killed >> already. I do not understand why should we care about any other context >> here? What is the actual problem this would solve? > > I agree with you, but still trying to understand what does Vlastimil mean > :). Well you wondered if we should stop caring about current, and I said that probably wouldn't be nice. As for caring about the other task, patch 3/7 does that for (MADV_COLD|MADV_PAGEOUT) so I just pointed out that the KSM case doesn't. AFAIU if we don't check the signals, we might be blocking the killed task from exiting? >> >> -- >> Michal Hocko >> SUSE Labs >> >