linux-kernel - Re: [PATCH] tracing: Do not synchronize freeing of trigger filter on boot up

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Date:   Tue, 13 Dec 2022 19:03:21 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] tracing: Do not synchronize freeing of trigger filter
 on boot up

On Wed, 14 Dec 2022 08:49:54 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> > Avoid calling the synchronization function when system_state is
> > SYSTEM_BOOTING.  
> 
> Shouldn't this be done inside tracepoint_synchronize_unregister()?
> Then, it will prevent similar warnings if we expand boot time feature.

I thought about that, but because this is a special case, I was thinking
that we don't just gloss over it and have something call this when it
shouldn't be in early boot up. I was surprised when it was called, and then
had to debug it a bit to figure out why it was. When I discovered the path
it took to get there, I realized it was legitimate.

Right now, I only see this one case as an exception. If more pop up that
are correct, then we can switch it over. But right now, I still want
calling tracepoint_synchronize_unregister() to warn if it is called in
early boot up, because that could be a sign that something went wrong.

-- Steve