Sysrq+f is used to kill a process either for debug or when the VM is
otherwise unresponsive.
It is not intended to trigger a panic when no process may be killed.
Avoid panicking the system for sysrq+f when no processes are killed.
Suggested-by: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
v2: no change
Documentation/sysrq.txt | 3 ++-
mm/oom_kill.c | 7 +++++--
2 files changed, 7 insertions(+), 3 deletions(-)
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");
}
- 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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