Messages in this thread | | | Date | Wed, 17 Jul 2013 16:43:57 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC PATCH 0/4] tracing: fix open/delete fixes |
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On 07/17, Masami Hiramatsu wrote: > > At a glance, you're trying to change which operation will be > failed. Currently, user can not remove an event while someone > opens files which related to the event. And this approach > changes that the someone can remove the event even if the > files are opened (and read/write operation will be failed). > Am I understand correctly?
Yes.
Once again, I am still not sure and I am asking for your review.
But to me this looks much better. To simplify the discussion, lets consider ftrace_enable_fops in particular.
- Why should .open() block rmdir or unregister_uprobe_event?
- Why do we need .open() at all? Whatever it can do to validate file/call/etc, .read/write can do the same.
- If we kill .open/release, we do not need the nontrivial refcounting. Everything becomes simple, no need to keep the state "in between".
We need event_mutex anyway (and note that other f_op's can also rely on other locks taken by trace_remove_event_call), the validation degrades to the trivial != NULL check.
- This also simplifies trace_remove_event_call() paths, we know that once it takes event_mutex nobody can play with ftrace_event_file/ftrace_event_call we are going to free.
Oleg.
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