oom: avoid killing kthreads if they assume the oom killed thread's mm
After selecting a task to kill, the oom killer iterates all processes and
kills all other threads that share the same mm_struct in different thread
groups. It would not otherwise be helpful to kill a thread if its memory
would not be subsequently freed.
A kernel thread, however, may assume a user thread's mm by using
use_mm(). This is only temporary and should not result in sending a
SIGKILL to that kthread.
This patch ensures that only user threads and not kthreads are sent a
SIGKILL if they share the same mm_struct as the oom killed task.
Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index d897262..b0d8943 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -439,7 +439,7 @@
task_unlock(p);
/*
- * Kill all processes sharing p->mm in other thread groups, if any.
+ * Kill all user processes sharing p->mm in other thread groups, if any.
* They don't get access to memory reserves or a higher scheduler
* priority, though, to avoid depletion of all memory or task
* starvation. This prevents mm->mmap_sem livelock when an oom killed
@@ -449,7 +449,8 @@
* signal.
*/
for_each_process(q)
- if (q->mm == mm && !same_thread_group(q, p)) {
+ if (q->mm == mm && !same_thread_group(q, p) &&
+ !(q->flags & PF_KTHREAD)) {
task_lock(q); /* Protect ->comm from prctl() */
pr_err("Kill process %d (%s) sharing same memory\n",
task_pid_nr(q), q->comm);