Re: [PATCH 2/6] relax sig_needs_tasklist()

Oleg Nesterov <[email protected]> writes:

> handle_stop_signal() does not need tasklist_lock for
> SIG_KERNEL_STOP_MASK signals anymore.

Small question.

If I read the code correctly the only thing handle_stop_signal needs
the tasklist_lock for is to protect task->parent, for the
do_notify_parent_cldstop(...) case.

If this is correct.  I think I see a path to kill read_lock(&tasklist_lock)
completely. 

- Protect task->parent with the rcu_read_lock && task_lock().
- Use the rcu forms of list_add/list_del on the tasklist.
- replace read_lock(&tasklist_lock) with rcu_read_lock().
- Make tasklist_lock a simple spin lock.

Comments?

Eric
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