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From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: paulmck@kernel.org, Joel Fernandes <joel@joelfernandes.org>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	mingo@kernel.org, gregkh@linuxfoundation.org,
	gustavo@embeddedor.com, tglx@linutronix.de,
	josh@joshtriplett.org, mathieu.desnoyers@efficios.com,
	jiangshanlai@gmail.com
Subject: Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}()
Date: Tue, 18 Feb 2020 12:46:09 -0500	[thread overview]
Message-ID: <20200218124609.1a33f868@gandalf.local.home> (raw)
In-Reply-To: <20200218133335.c87d7b2399ee6532bf28b74a@kernel.org>

On Tue, 18 Feb 2020 13:33:35 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> On Mon, 17 Feb 2020 08:31:12 -0800
> "Paul E. McKenney" <paulmck@kernel.org> wrote:
> >   
> > > BTW, if you consider the x86 specific code is in the generic file,
> > > we can move NOKPROBE_SYMBOL() in arch/x86/kernel/traps.c.
> > > (Sorry, I've hit this idea right now)  
> > 
> > Might this affect other architectures with NMIs and probe-like things?
> > If so, it might make sense to leave it where it is.  
> 
> Yes, git grep shows that arm64 is using rcu_nmi_enter() in
> debug_exception_enter().
> OK, let's keep it, but maybe it is good to update the comment for
> arm64 too. What about following?
> 
> +/*
> + * All functions in do_int3() on x86, do_debug_exception() on arm64 must be
> + * marked NOKPROBE before kprobes handler is called.
> + * ist_enter() on x86 and debug_exception_enter() on arm64 which is called
> + * before kprobes handle happens to call rcu_nmi_enter() which means
> + * that rcu_nmi_enter() must be marked NOKRPOBE.
> + */
> 

Ah, why don't we just say...

/*
 * All functions called in the breakpoint trap handler (e.g. do_int3()
 * on x86), must not allow kprobes until the kprobe breakpoint handler
 * is called, otherwise it can cause an infinite recursion.
 * On some archs, rcu_nmi_enter() is called in the breakpoint handler
 * before the kprobe breakpoint handler is called, thus it must be
 * marked as NOKPROBE.
 */

And that way we don't make this an arch specific comment.

-- Steve

  parent reply	other threads:[~2020-02-18 17:46 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-12 21:01 [PATCH v2 0/9] tracing vs rcu vs nmi Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 1/9] rcu: Rename rcu_irq_{enter,exit}_irqson() Peter Zijlstra
2020-02-12 22:38   ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 2/9] rcu: Mark rcu_dynticks_curr_cpu_in_eqs() inline Peter Zijlstra
2020-02-12 22:38   ` Joel Fernandes
2020-02-13  1:41     ` Steven Rostedt
2020-02-13 14:25       ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12 23:20   ` Joel Fernandes
2020-02-13  8:27     ` Peter Zijlstra
2020-02-13 13:31       ` Joel Fernandes
2020-02-13 13:51       ` Paul E. McKenney
2020-02-13 16:40         ` Peter Zijlstra
2020-02-13 18:56           ` Paul E. McKenney
2020-02-13 20:44             ` Joel Fernandes
2020-02-13 20:54               ` Paul E. McKenney
2020-02-13 21:19                 ` Joel Fernandes
2020-02-13 21:38                   ` Steven Rostedt
2020-02-13 21:50                     ` Paul E. McKenney
2020-02-13 22:04                       ` Steven Rostedt
2020-02-13 22:39                         ` Paul E. McKenney
2020-02-14  6:19                           ` Masami Hiramatsu
2020-02-15 14:59                             ` Paul E. McKenney
2020-02-17  8:55                               ` Masami Hiramatsu
2020-02-17 16:31                                 ` Paul E. McKenney
2020-02-18  4:33                                   ` Masami Hiramatsu
2020-02-18 16:12                                     ` Paul E. McKenney
2020-02-18 16:15                                       ` Mathieu Desnoyers
2020-02-18 16:35                                       ` Steven Rostedt
2020-02-18 17:46                                     ` Steven Rostedt [this message]
2020-02-18 20:18                                       ` Paul E. McKenney
2020-02-19  2:45                                         ` Masami Hiramatsu
2020-03-06 18:01                                           ` Masami Hiramatsu
2020-03-06 18:47                                             ` Joel Fernandes
2020-03-06 19:11                                             ` Joel Fernandes
2020-03-07  1:58                                               ` Masami Hiramatsu
2020-03-06  0:42                     ` Thomas Gleixner
2020-02-13 21:48                   ` Paul E. McKenney
2020-02-13 22:58                     ` Joel Fernandes
2020-02-13 23:55                       ` Steven Rostedt
2020-02-18 19:58               ` Peter Zijlstra
2020-02-18 20:17                 ` Paul E. McKenney
2020-02-18 20:40                   ` Peter Zijlstra
2020-02-18 21:39                     ` Paul E. McKenney
2020-02-19  9:57                       ` Peter Zijlstra
2020-02-19 12:46                         ` Paul E. McKenney
2020-02-12 23:27   ` Joel Fernandes
2020-02-13  8:28     ` Peter Zijlstra
2020-02-13 18:39       ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 4/9] sched,rcu,tracing: Avoid tracing before in_nmi() is correct Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 5/9] x86,tracing: Add comments to do_nmi() Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 6/9] perf,tracing: Prepare the perf-trace interface for RCU changes Peter Zijlstra
2020-02-12 23:28   ` Joel Fernandes
2020-02-13  8:29     ` Peter Zijlstra
2020-02-13 18:38       ` Joel Fernandes
2020-02-12 21:01 ` [PATCH v2 7/9] tracing: Employ trace_rcu_{enter,exit}() Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 8/9] tracing: Remove regular RCU context for _rcuidle tracepoints (again) Peter Zijlstra
2020-02-12 21:01 ` [PATCH v2 9/9] perf,tracing: Allow function tracing when !RCU Peter Zijlstra
2020-02-14  2:28   ` Sergey Senozhatsky
2020-02-14  2:42     ` Sergey Senozhatsky
2020-02-14  3:32       ` Steven Rostedt
2020-02-14 20:38   ` Kim Phillips
2020-02-14 22:48     ` Steven Rostedt

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