Re: [PATCH v2 4/4] tracing/kprobes: Turn trace_probe->files intolist_head
From: Steven Rostedt
Date: Mon Jul 01 2013 - 15:55:36 EST
On Mon, 2013年07月01日 at 21:36 +0200, Oleg Nesterov wrote:
>
On 07/01, Steven Rostedt wrote:
>
>
>
> On Thu, 2013年06月20日 at 19:38 +0200, Oleg Nesterov wrote:
>
>
>
> > -static int
>
> > -trace_probe_file_index(struct trace_probe *tp, struct ftrace_event_file *file)
>
> > +static struct event_file_link *
>
> > +find_event_file_link(struct trace_probe *tp, struct ftrace_event_file *file)
>
> > {
>
> > - struct ftrace_event_file **files;
>
> > - int i;
>
> > + struct event_file_link *link;
>
> >
>
> > - /*
>
> > - * Since all tp->files updater is protected by probe_enable_lock,
>
> > - * we don't need to lock an rcu_read_lock.
>
> > - */
>
> > - files = rcu_dereference_raw(tp->files);
>
> > - if (files) {
>
> > - for (i = 0; files[i]; i++)
>
> > - if (files[i] == file)
>
> > - return i;
>
> > - }
>
> > + list_for_each_entry(link, &tp->files, list)
>
> > + if (link->file == file)
>
> > + return link;
>
>
>
> Shouldn't that be list_for_each_entry_rcu()?
>
>
No.
>
>
This is the writer which modifies the list. enable/disable_trace_probe
>
should be serialized wrt each other / itself anyway, otherwise they are
>
buggy in any case.
Ah OK, I missed the readers of kprobe*_trace_func() and was confused by
the other rcu usage. Nevermind.
-- Steve
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