From: "Paul E. McKenney" <paulmck@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
kim.phillips@amd.com
Subject: Re: [PATCH] rcu,ftrace: Fix ftrace recursion
Date: Tue, 29 Sep 2020 07:41:06 -0700 [thread overview]
Message-ID: <20200929144105.GU29330@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200929103620.06762622@gandalf.local.home>
On Tue, Sep 29, 2020 at 10:36:20AM -0400, Steven Rostedt wrote:
> On Tue, 29 Sep 2020 13:33:40 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > Kim reported that perf-ftrace made his box unhappy. It turns out that
> > commit:
> >
> > ff5c4f5cad33 ("rcu/tree: Mark the idle relevant functions noinstr")
> >
> > removed one too many notrace. Probably due to there not being a helpful
> > comment.
> >
> > Reinstate the notrace and add a comment to avoid loosing it again.
> >
> > Fixes: ff5c4f5cad33 ("rcu/tree: Mark the idle relevant functions noinstr")
> > Reported-by: Kim Phillips <kim.phillips@amd.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> > kernel/rcu/tree.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index ee5e595501e8..33020d84ec6b 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -1098,8 +1098,11 @@ noinstr bool __rcu_is_watching(void)
> > * CPU can safely enter RCU read-side critical sections. In other words,
> > * if the current CPU is not in its idle loop or is in an interrupt or
> > * NMI handler, return true.
> > + *
> > + * Must be notrace because __ftrace_ops_list_func() / ftrace_ops_assist_func()
> > + * will call this (for every function) outside of recursion protection.
> > */
> > -bool rcu_is_watching(void)
> > +notrace bool rcu_is_watching(void)
> > {
> > bool ret;
> >
>
> I think the patch I suggested is more suitable.
OK, I will let you guys fight it out. ;-)
Thanx, Paul
next prev parent reply other threads:[~2020-09-29 14:41 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-29 11:33 [PATCH] rcu,ftrace: Fix ftrace recursion Peter Zijlstra
2020-09-29 14:31 ` Paul E. McKenney
2020-09-29 14:36 ` Steven Rostedt
2020-09-29 14:41 ` Paul E. McKenney [this message]
2020-09-29 14:54 ` Steven Rostedt
2020-09-29 16:56 ` Paul E. McKenney
2020-09-29 17:04 ` Steven Rostedt
2020-10-05 0:18 ` Paul E. McKenney
2020-09-29 14:49 ` Peter Zijlstra
2020-09-29 15:19 ` Steven Rostedt
2020-09-29 14:43 ` Kim Phillips
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