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SubjectRe: [PATCH 5/5] tracing: reset iterator in t_start()
> Another version:
> Since we have saved current (struct tracer *) in m->private in .next, in
> .start, we don't need to call .next to find the one that should be
> printed in 2nd or nth time.
>

I don't like this for 2 reasons.

1. It's strange that @pos is not incremented in next().

2.
t_stop()
mutex_unlock()
unregister_tracer(t)
t_start()
mutex_lock()
t = m->private
...
t = t-next.

We access t->next though @t was unregistered. This is not
good, though it does no harm here.

> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index cae34c6..02cdccc 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2055,8 +2055,6 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
> {
> struct tracer *t = m->private;
>
> - (*pos)++;
> -
> if (t)
> t = t->next;
>
> @@ -2068,11 +2066,8 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
> static void *t_start(struct seq_file *m, loff_t *pos)
> {
> struct tracer *t = m->private;
> - loff_t l = 0;
>
> mutex_lock(&trace_types_lock);
> - for (; t && l < *pos; t = t_next(m, t, &l))
> - ;
>
> return t;
> }
>
>


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