linux-kernel - Re: [PATCH v4 1/5] tracing: Introduce faultable tracepoints

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Message-ID: <fc50b15e-8ad1-4ed5-b833-fd3b72c0aa0e@paulmck-laptop>
Date:   Tue, 21 Nov 2023 08:45:22 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org,
        Michael Jeanson <mjeanson@...icios.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Yonghong Song <yhs@...com>, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>, bpf@...r.kernel.org,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH v4 1/5] tracing: Introduce faultable tracepoints

On Tue, Nov 21, 2023 at 09:44:44AM -0500, Steven Rostedt wrote:
> On Tue, 21 Nov 2023 15:36:47 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > Still utterly confused about what task-tracing rcu is and how it is
> > different from preemptible rcu.
> 
> Is this similar to synchronize_rcu_tasks()? As I understand that one (grace
> period continues until all tasks have voluntarily scheduled or gone into
> user space). But I'm a bit confused by synchronize_rcu_tasks_trace()?
> 
> Note, that for syncronize_rcu_tasks() the critical sections must not call
> schedule (although it is OK to be preempted).

The synchronize_rcu_tasks() and synchronize_rcu_tasks_trace() functions
are quite different, as noted elsewhere in this thread.

							Thanx, Paul