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

From: Chris Down
Date: Wed Sep 09 2020 - 17:56:24 EST

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

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!