Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 18 Oct 2022 11:22:24 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc:     "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
        Shuah Khan <shuah@kernel.org>, <linux-kernel@vger.kernel.org>,
        Akanksha J N <akanksha@linux.vnet.ibm.com>
Subject: Re: [PATCH] selftests/ftrace: Limit number of lines processed in
 'trace'
Message-ID: <20221018112224.372a3484@gandalf.local.home>
In-Reply-To: <20221019001949.950fb044677f96c6cdd00fdf@kernel.org>
References: <20221017105502.307506-1-naveen.n.rao@linux.vnet.ibm.com>
        <20221017105103.540a87c7@gandalf.local.home>
        <20221019001949.950fb044677f96c6cdd00fdf@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

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