On 06/09, Michal Hocko wrote:
>
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1883,6 +1883,32 @@ extern int arch_task_struct_size __read_mostly;
> #define TNF_FAULT_LOCAL 0x08
> #define TNF_MIGRATE_FAIL 0x10
>
> +static inline bool in_vfork(struct task_struct *tsk)
> +{
> + bool ret;
> +
> + /*
> + * need RCU to access ->real_parent if CLONE_VM was used along with
> + * CLONE_PARENT.
> + *
> + * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
> + * imply CLONE_VM
> + *
> + * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
> + * ->real_parent is not necessarily the task doing vfork(), so in
> + * theory we can't rely on task_lock() if we want to dereference it.
> + *
> + * And in this case we can't trust the real_parent->mm == tsk->mm
> + * check, it can be false negative. But we do not care, if init or
> + * another oom-unkillable task does this it should blame itself.
> + */
> + rcu_read_lock();
> + ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
> + rcu_read_unlock();
> +
> + return ret;
> +}
ACK, but why sched.h ? It has a single caller in oom_kill.c.
Oleg.
