Re: [PATCH] ring-buffer: fix uninitialized read_stamp

[David Sharp]

On Fri, Jun 22, 2012 at 6:27 PM, David Sharp <dhsharp@xxxxxxxxxx> wrote:
> On Fri, Jun 22, 2012 at 4:31 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>>
>> Now I think you may understand my patch.
>
> Yeah, mostly. At least enough that I think it's worth testing. But Monday.

I got around to testing your patch today, and it fixes the issue. No
bad-looking timestamps in 40 runs, whereas could reproduce within 3
runs before. Do you want me to send you a fresh patch, or just use the
one you have?

>>> On Thu, Jun 21, 2012 at 8:56 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>>> > Does something like this work for you. Note, this is totally untested!
>>> >
>>> > -- Steve
>>> >
>>> > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
>>> > index ad0239b..5943044 100644
>>> > --- a/kernel/trace/ring_buffer.c
>>> > +++ b/kernel/trace/ring_buffer.c
>>> > @@ -3246,6 +3246,10 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
>>> > Â Â Â Âif (cpu_buffer->commit_page == cpu_buffer->reader_page)
>>> > Â Â Â Â Â Â Â Âgoto out;
>>> >
>>> > + Â Â Â /* Don't bother swapping if the ring buffer is empty */
>>> > + Â Â Â if (rb_num_of_entries(cpu_buffer) == 0)
>>> > + Â Â Â Â Â Â Â goto out;
>>> > +
>>> > Â Â Â Â/*
>>> > Â Â Â Â * Reset the reader page to size zero.
>>> > Â Â Â Â */
--
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