Messages in this thread | | | From | David Sharp <> | Date | Wed, 27 Jun 2012 11:00:30 -0700 | Subject | Re: [PATCH] ring-buffer: fix uninitialized read_stamp |
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On Wed, Jun 27, 2012 at 5:46 AM, Steven Rostedt <rostedt@goodmis.org> wrote: > On Tue, 2012-06-26 at 17:35 -0700, David Sharp wrote: > > On Fri, Jun 22, 2012 at 6:27 PM, David Sharp <dhsharp@google.com> wrote: > > > On Fri, Jun 22, 2012 at 4:31 PM, Steven Rostedt <rostedt@goodmis.org> 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? > > I rather use this one for two reasons.
I just meant, do you want me to send you a version of your patch with my description (I'll update it, obviously), or do it yourself.
> > 1) it limits the places where read_stamp is updated. And I rather not > add an update because "it fixes an anomaly". > > 2) I think it is wrong to force the writer on the reader page when no > write has been made. There's some side effects that this causes. One is > that if you do a read with no write, and then do nothing, it forces the > writer on that page. Now if a lot of writes happen (function tracing), > the writes that were on the reader page are never overwritten when the > buffer is full. Then you get a page of very old data, followed by a > buffer full of new data.
I have always disliked that page of very old data, so I'm really happy that this will get rid of it. As I recall, you once claimed this was a "feature". :)
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