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SubjectRe: [PATCH][git pull] tracing: limit the number of loops the ring buffer self test can make

* Steven Rostedt <rostedt@goodmis.org> wrote:

> Ingo,
>
> I added one more fix. Thinking about the solution, although
> the disabling of the ring buffer is good enough to prevent the
> bug you hit. I became worried about a corrupted ring buffer
> that can cause an inifinite loop. This patch adds a fix for
> that too.

yes, that's a good idea too:

> @@ -23,10 +23,20 @@ static int trace_test_buffer_cpu(struct trace_array *tr, int cpu)
> {
> struct ring_buffer_event *event;
> struct trace_entry *entry;
> + unsigned int loops = 0;
>
> while ((event = ring_buffer_consume(tr->buffer, cpu, NULL))) {
> entry = ring_buffer_event_data(event);
>
> + /*
> + * The ring buffer is a size of trace_buf_size, if
> + * we loop more than the size, there's something wrong
> + * with the ring buffer.
> + */
> + if (loops++ > trace_buf_size) {
> + printk(KERN_CONT ".. bad ring buffer ");
> + goto failed;
> + }

Would be nice to also emit a WARN_ONCE() message about the test
failure, to make sure automated tests like mine pick even
soft-failures up.

Ingo


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