linux-kernel - Re: [PATCH] ring-buffer: Fix polling on trace

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Message-ID: <20140626205327.5b526302@gandalf.local.home>
Date:	Thu, 26 Jun 2014 20:53:27 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Martin Lau <kafai@...com>
Cc:	<linux-kernel@...r.kernel.org>, <clm@...com>
Subject: Re: [PATCH] ring-buffer: Fix polling on trace_pipe

On Thu, 26 Jun 2014 11:34:46 -0700
Martin Lau <kafai@...com> wrote:

> Hi Steve,
> 
> Can the modified test program reproduce the problem in your test setup?

Ah sorry, got distracted by other work.

OK, I just tried it out, and here's my results:

I ran you code with my current kernel and this is what I got:

# ./ftrace-test-epoll-kafai 
           <...>-3183  [002] ...1    81.777891: tracing_mark_write:
some data 3183: waitting for more data......
3184: written more data

And it just hung there.


Then I applied your patch, compiled and booted it, and ran the test
again, and I got this:

# ./ftrace-test-epoll-kafai

It just hung there. No forward progress.

I don't think that was the result you intended.

-- Steve


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