Messages in this thread | | | Date | Tue, 14 Jul 2015 14:16:18 -0700 (PDT) | From | David Rientjes <> | Subject | RE: [patch v3 3/3] mm, oom: do not panic for oom kills triggered from sysrq |
| |
On Fri, 10 Jul 2015, Hillf Danton wrote:
> > 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; >
I'm still not sure I understand your point, unfortunately. The new check:
if (!p && oc->order != -1) { dump_header(oc, NULL, NULL); panic("Out of memory and no killable processes...\n"); }
ensures we never panic when called from sysrq. This is done because userspace can easily race when there is a single eligible process to kill that exits or is otherwise killed and the sysrq+f ends up panicking the machine unexpectedly.
| |