On Mon 25-07-11 17:12:37, David Rientjes wrote:
> 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.
Good catch. Have you ever seen this happening?
>
> 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@xxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> ---
> mm/oom_kill.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -433,7 +433,7 @@ 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
> @@ -443,7 +443,8 @@ 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);
>
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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