On 04/12, Michal Hocko wrote:
>
> We shouldn't consider the task
> unless the whole thread group is going down.
Yes, agreed. I'd even say that oom-killer should never look at individual
task/threads, it should work with mm's. And one of the big mistakes (imo)
was the s/for_each_process/for_each_thread/ change in select_bad_process()
a while ago.
Michal, I won't even try to actually review this patch, I lost any hope
to understand OOM-killer a long ago ;) But I do agree with this change,
we obviously should not rely on PF_EXITING.
> static inline bool task_will_free_mem(struct task_struct *task)
> {
> + struct signal_struct *sig = task->signal;
> +
> /*
> * A coredumping process may sleep for an extended period in exit_mm(),
> * so the oom killer cannot assume that the process will promptly exit
> * and release memory.
> */
> - return (task->flags & PF_EXITING) &&
> - !(task->signal->flags & SIGNAL_GROUP_COREDUMP);
> + if (sig->flags & SIGNAL_GROUP_COREDUMP)
> + return false;
> +
> + if (!(task->flags & PF_EXITING))
> + return false;
> +
> + /* Make sure that the whole thread group is going down */
> + if (!thread_group_empty(task) && !(sig->flags & SIGNAL_GROUP_EXIT))
> + return false;
> +
> + return true;
So this looks certainly better to me, but perhaps it should do
if (SIGNAL_GROUP_COREDUMP)
return false;
if (SIGNAL_GROUP_EXIT)
return true;
if (thread_group_empty() && PF_EXITING)
return true;
return false;
?
I won't insist, I do not even know if this would be better or not. But if
SIGNAL_GROUP_EXIT is set all sub-threads should go away even if PF_EXITING
is not set yet because this task didn't dequeue SIGKILL yet.
Up to you in any case.
Oleg.
