Re: ftrace multibuffer && rcu (Was: tracing/uprobes: Support ftrace_event_file base multibuffer)

[Oleg Nesterov <oleg@redhat.com>]

On 06/14, Oleg Nesterov wrote:
>
> So perhaps something like below (untested) makes sense? With this patch
> we can trivially convert trace_kprobe.c to use list_add/del/each_rcu.

Forgot to mention, the patch is obviously incomplete, __kprobe_trace_func()
can see the "dead" file even if its memory can't go away. But this looks
fixable.

> +static inline struct event_file_link *
> +alloc_event_file_link(struct ftrace_event_file *file)
> +{
> +	struct event_file_link *link = kmalloc(sizeof(*link), GFP_KERNEL);
> +	if (link)
> +		link->file = file;
> +	return link;
> +}

And this lacks atomic_inc(file->refcnt).

In short, this is just to explain what I meant, the actual change should
probably differ.

Oleg.