linux-kernel - Re: [PATCH] selftests/ftrace: Limit number of lines processed in 'trace'

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Date:   Tue, 18 Oct 2022 11:22:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Shuah Khan <shuah@...nel.org>, <linux-kernel@...r.kernel.org>,
        Akanksha J N <akanksha@...ux.vnet.ibm.com>
Subject: Re: [PATCH] selftests/ftrace: Limit number of lines processed in
 'trace'

On Wed, 19 Oct 2022 00:19:49 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> > You need to make sure that the "pause-on-trace" option is set or tracing_on
> > is set to 0 (disabled). Otherwise, if the tracing is still active, then the
> > reading of the trace file could potentially never end.  
> 
> initialize_ftrace() does this setting. So it must be set.
> If you run the ftracetest on old kernel, this feature is not there and
> it may cause a trouble. Naveen, can you clarify it?

But for old kernels that do not have "pause-on-trace" it should be the
default. The "pause-on-trace" was added when the default was changed to not
pause the trace while reading it.

-- Steve