On 09/22, Linus Torvalds wrote:
>
> However, this now becomes a pattern for the series, and that just makes me 
> think
>
>     "Why is this not a 'for_each_mm()' pattern helper?"

And we already have other users. And note that oom_kill_process() does _not_
follow this pattern and that is why it is buggy.

So this is funny, but I was thinking about almost the same, something like

        struct task_struct *next_task_with_mm(struct task_struct *p)
        {
                struct task_struct *t;

                p = p->group_leader;
                while ((p = next_task(p)) != &init_task) {
                        if (p->flags & PF_KTHREAD)
                                continue;

                        t = find_lock_task_mm(p);
                        if (t)
                                return t;
                }

                return NULL;
        }

        #define for_each_task_lock_mm(p)
                for (p = &init_task; (p = next_task_with_mm(p)); task_unlock(p))


So that you can do

        for_each_task_lock_mm(p) {
                do_something_with(p->mm);

                if (some_condition()) {
                        // UNFORTUNATELY you can't just do "break"
                        task_unlock(p);
                        break;
                }
        }

do you think it makes sense?


In fact it can't be simpler, we can move task_unlock() into next_task_with_mm(),
it can check ->mm != NULL or p != init_task.

Oleg.

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