linux-kernel - Re: [PATCH V4 04/19] trace/osnoise: Support a list of trace

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Message-ID: <20211025093541.6ced3995@gandalf.local.home>
Date:   Mon, 25 Oct 2021 09:35:41 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Daniel Bristot de Oliveira <bristot@...nel.org>
Cc:     paulmck@...nel.org, Ingo Molnar <mingo@...hat.com>,
        Tom Zanussi <zanussi@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        John Kacur <jkacur@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-rt-users@...r.kernel.org, linux-trace-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 04/19] trace/osnoise: Support a list of trace_array
 *tr

On Mon, 25 Oct 2021 11:10:26 +0200
Daniel Bristot de Oliveira <bristot@...nel.org> wrote:

> The start/stop/reset operations are called from trace "core" operations. So they
> are all protected/serialized by trace_types_lock (by trace/core).
> 
> So, it seems that the way to go is to remove the rcu_read_lock/unlock() from
> unregister, adding a lockdep check to see if trace_types_lock is help as a bonus?

Yes, I would recommend the lockdep assert added. This way it also documents
what lock protects modification of the list.

Thanks,

-- Steve