Re: linux-next: stall warnings and deadlock on Arm64 (was: [PATCH] kfence: Avoid stalling...)

Steven Rostedt
2020-11-20T19:16:48Z

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