> > > diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt
> > > --- a/Documentation/sysrq.txt
> > > +++ b/Documentation/sysrq.txt
> > > @@ -75,7 +75,8 @@ On all - write a character to /proc/sysrq-trigger. e.g.:
> > >
> > > 'e' - Send a SIGTERM to all processes, except for init.
> > >
> > > -'f' - Will call oom_kill to kill a memory hog process.
> > > +'f' - Will call the oom killer to kill a memory hog process, but do not
> > > + panic if nothing can be killed.
> > >
> > > 'g' - Used by kgdb (kernel debugger)
> > >
> > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > --- a/mm/oom_kill.c
> > > +++ b/mm/oom_kill.c
> > > @@ -607,6 +607,9 @@ void check_panic_on_oom(struct oom_control *oc, enum oom_constraint constraint,
> > > if (constraint != CONSTRAINT_NONE)
> > > return;
> > > }
> > > + /* Do not panic for oom kills triggered by sysrq */
> > > + if (oc->order == -1)
> > > + return;
> > > dump_header(oc, NULL, memcg);
> > > panic("Out of memory: %s panic_on_oom is enabled\n",
> > > sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
> > > @@ -686,11 +689,11 @@ bool out_of_memory(struct oom_control *oc)
> > >
> > > p = select_bad_process(oc, &points, totalpages);
> > > /* Found nothing?!?! Either we hang forever, or we panic. */
> > > - if (!p) {
> > > + if (!p && oc->order != -1) {
> > > dump_header(oc, NULL, NULL);
> > > panic("Out of memory and no killable processes...\n");
> > > }
> >
> > Given sysctl_panic_on_oom checked, AFAICU there seems
> > no chance for panic, no matter -1 or not.
> >
>
> I'm not sure I understand your point.
>
> There are two oom killer panics: when panic_on_oom is enabled and when the
> oom killer can't find an eligible process.
>
> The change to the panic_on_oom panic is dealt with in check_panic_on_oom()
> and the no eligible process panic is dealt with here.
>
> If the sysctl is disabled, and there are no eligible processes to kill,
> the change in behavior here is that we don't panic when triggered from
> sysrq. That's the change in the hunk above.
>
When no eligible processes is selected to kill, we are sure that we skip one
panic in check_panic_on_oom(), and we have no clear reason to panic again.
But we can simply answer the caller that there is no page, and let her
decide what to do.
So I prefer to fold the two panic into one.
Hillf
> > > - if (p != (void *)-1UL) {
> > > + if (p && p != (void *)-1UL) {
> > > oom_kill_process(oc, p, points, totalpages, NULL,
> > > "Out of memory");
> > > killed = 1;
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