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Date:   Fri, 20 Nov 2020 14:16:39 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Marco Elver <elver@google.com>
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        Anders Roxell <anders.roxell@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Jann Horn <jannh@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        kasan-dev <kasan-dev@googlegroups.com>, rcu@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Tejun Heo <tj@kernel.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        linux-arm-kernel@lists.infradead.org
Subject: Re: linux-next: stall warnings and deadlock on Arm64 (was: [PATCH]
 kfence: Avoid stalling...)
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On Fri, 20 Nov 2020 19:17:37 +0100
Marco Elver <elver@google.com> wrote:

> > > +++ b/kernel/rcu/Makefile
> > > @@ -3,6 +3,13 @@
> > >  # and is generally not a function of system call inputs.
> > >  KCOV_INSTRUMENT := n
> > >  
> > > +ifdef CONFIG_FUNCTION_TRACER
> > > +CFLAGS_REMOVE_update.o = $(CC_FLAGS_FTRACE)
> > > +CFLAGS_REMOVE_sync.o = $(CC_FLAGS_FTRACE)
> > > +CFLAGS_REMOVE_srcutree.o = $(CC_FLAGS_FTRACE)
> > > +CFLAGS_REMOVE_tree.o = $(CC_FLAGS_FTRACE)
> > > +endif
> > > +  
> > 
> > Can you narrow it down further? That is, do you really need all of the
> > above to stop the stalls?  
> 
> I tried to reduce it to 1 or combinations of 2 files only, but that
> didn't work.

I'm curious if this would help at all?


diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2a52f42f64b6..d020ecefd151 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1094,7 +1094,7 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
  * if the current CPU is not in its idle loop or is in an interrupt or
  * NMI handler, return true.
  */
-bool rcu_is_watching(void)
+notrace bool rcu_is_watching(void)
 {
 	bool ret;
 
Although I don't see it in the recursion list.

-- Steve