Re: [PATCH v2] mm/vmscan: fix infinite loop in drop_slab_node

[Chris Down]

Matthew Wilcox writes:
> On Wed, Sep 09, 2020 at 10:47:24PM +0100, Chris Down wrote:
> > Vlastimil Babka writes:
> > > - Exit also on other signals such as SIGABRT, SIGTERM? If I write to drop_caches
> > > and think it's too long, I would prefer to kill it by ctrl-c and not just kill
> >
> > Oh dear, fatal_signal_pending() doesn't consider cases with no more
> > userspace instructions due to SIG_DFL on TERM/INT etc, that seems misleading
> > :-( I had (naively) believed it internally checks the same set as
> > TASK_KILLABLE.
> >
> > Chuxin, Muchun, can you please make it work using TASK_KILLABLE in a similar
> > way to how schedule_timeout_killable and friends do it instead, so that
> > other signals will be caught?
>
> You're mistaken.
>
>        if (sig_fatal(p, sig) &&
>            !(signal->flags & SIGNAL_GROUP_EXIT) &&
>            !sigismember(&t->real_blocked, sig) &&
>            (sig == SIGKILL || !p->ptrace)) {
> ...
>                                sigaddset(&t->pending.signal, SIGKILL);
>
> static inline int __fatal_signal_pending(struct task_struct *p)
> {
>        return unlikely(sigismember(&p->pending.signal, SIGKILL));
> }

Oh great, that makes things way easier. Thanks!