Messages in this thread | | | Subject | Re: lockup in rb_get_reader_page | From | Steven Rostedt <> | Date | Tue, 30 Mar 2010 20:35:24 -0400 |
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Hi Jiaying,
On Tue, 2010-03-30 at 16:27 -0700, Jiaying Zhang wrote: > Hi Steven, > > We recently saw some cpu lockups while running kernel tracing. > The problem started to happen after we synced up our ring buffer > code with the upstream lockless ring buffer change. It usually > took many hours and heavy trace load to hit this problem. When > the lockup happens, the problematic cpu seemed to be in an infinite > loop of trying to grab the head_page in rb_get_reader_page(). > > We would like to check with you on whether this is a known issue. > If so, do we have a bug fix? If not, do you have any suggestions on > where we should check?
I'm unaware of any problems with the ring buffer. I've been running the lockless version for over a year now, and hammering it with very intensive tracing.
Now, you see this on the reader side. There has been a few recent fixes that could cause problems when we have multiple readers. Ftrace usage does not usually encounter multiple readers so I have not had issues. But Li Zefan had a stress test that did find and trigger the problems.
Are you using the latest ring buffer that is in Linus's tree? Are you resetting the ring buffer while reading it?
I guess I need to know more exactly what you are doing to understand the problem.
Thanks,
-- Steve
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