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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>
This commit is contained in:
David Rientjes 2011-10-31 17:07:11 -07:00 committed by Linus Torvalds
parent f660daac47
commit 7b0d44fa49
1 changed files with 3 additions and 2 deletions
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5
mm/oom_kill.c
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@ -439,7 +439,7 @@ static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
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 @@ static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
* 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);