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Date:   Mon, 22 May 2023 07:57:00 -0700
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Stephen Rothwell <sfr@canb.auug.org.au>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Next Mailing List <linux-next@vger.kernel.org>
Subject: Re: linux-next: build failure after merge of the rcu tree
Message-ID: <2a55ce77-75ec-461d-9050-696c2537619b@paulmck-laptop>
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On Mon, May 22, 2023 at 11:45:03AM +1000, Stephen Rothwell wrote:
> Hi Paul,
> 
> On Thu, 18 May 2023 19:12:52 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:
> >
> > On Fri, May 19, 2023 at 10:59:50AM +1000, Stephen Rothwell wrote:
> > > Hi all,
> > > 
> > > After merging the rcu tree, today's linux-next build (x86_64 allmodconfig)
> > > failed like this:
> > > 
> > > kernel/rcu/rcuscale.c:340:27: error: 'get_rcu_tasks_trace_gp_kthread' undeclared here (not in a function); did you mean 'show_rcu_tasks_trace_gp_kthread'?
> > >   340 |         .rso_gp_kthread = get_rcu_tasks_trace_gp_kthread,
> > >       |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >       |                           show_rcu_tasks_trace_gp_kthread
> > > 
> > > Caused by commit
> > > 
> > >   9bb839a83e1b ("rcuscale: Measure grace-period kthread CPU time")
> > > 
> > > CONFIG_RCU_SCALE_TEST=m
> > > 
> > > I have used the rcu tree from next-20230518 for today.  
> > 
> > Huh.  Modules and #ifdefs trip me up again.  Will fix, and thank you
> > for catching it!
> 
> This is now:
> 
> ERROR: modpost: "get_rcu_tasks_trace_gp_kthread" [kernel/rcu/rcuscale.ko] undefined!
> 
> I have used the rcu tree from next-20230518 again for today.

-ENOREPRODUCE

Perhaps the #ifdef around its definition is causing trouble in your
environment.  And to be fair, the small-memory systems that might not
want that function unconditionally defined could do even better by not
configuring anything requiring Tasks Trace RCU.

I will adjust.  Here is hoping!

							Thanx, Paul