linux-kernel - Re: [PATCH] rcu-tasks: Fix compilation warning with !CONFIG_TASKS_RCU and CONFIG_TINY

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Message-ID: <20200917232416.GR29330@paulmck-ThinkPad-P72>
Date:   Thu, 17 Sep 2020 16:24:16 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu-tasks: Fix compilation warning with
 !CONFIG_TASKS_RCU and CONFIG_TINY_RCU

On Fri, Sep 18, 2020 at 01:26:41AM +0300, Laurent Pinchart wrote:
> Hi Paul,
> 
> On Tue, Aug 25, 2020 at 09:16:29AM -0700, Paul E. McKenney wrote:
> > On Tue, Aug 25, 2020 at 06:22:49PM +0300, Laurent Pinchart wrote:
> > > On Tue, Aug 25, 2020 at 08:02:22AM -0700, Paul E. McKenney wrote:
> > > > On Sun, Aug 23, 2020 at 06:04:05AM +0300, Laurent Pinchart wrote:
> > > > > Commit 8344496e8b49 ("rcu-tasks: Conditionally compile
> > > > > show_rcu_tasks_gp_kthreads()") introduced conditional compilation of
> > > > > several functions, but forgot one occurrence of
> > > > > show_rcu_tasks_classic_gp_kthread() that causes the compiler to warn of
> > > > > an unused static function. Fix it.
> > > > > 
> > > > > Fixes: 8344496e8b49 ("rcu-tasks: Conditionally compile show_rcu_tasks_gp_kthreads()")
> > > > > Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > > > > ---
> > > > >  kernel/rcu/tasks.h | 2 ++
> > > > >  1 file changed, 2 insertions(+)
> > > > > 
> > > > > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> > > > > index 835e2df8590a..bddf3968c1eb 100644
> > > > > --- a/kernel/rcu/tasks.h
> > > > > +++ b/kernel/rcu/tasks.h
> > > > > @@ -590,7 +590,9 @@ void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
> > > > >  }
> > > > >  
> > > > >  #else /* #ifdef CONFIG_TASKS_RCU */
> > > > > +#ifndef CONFIG_TINY_RCU
> > > > >  static void show_rcu_tasks_classic_gp_kthread(void) { }
> > > > > +#endif /* #ifndef CONFIG_TINY_RCU */
> > > > >  void exit_tasks_rcu_start(void) { }
> > > > >  void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
> > > > >  #endif /* #else #ifdef CONFIG_TASKS_RCU */
> > > > 
> > > > Good catch!!!
> > > > 
> > > > But does the following addition of "static inline" work for you?
> > > 
> > > They do. I initially added a static inline, and realized #ifdef was used
> > > extensively when trying to find the proper Fixes: tag, so I went for
> > > that. I don't mind either way, as long as this gets fixed :-)
> > 
> > This is admittedly an odd .h file, given that it is included but once.
> > 
> > I have applied the following patch with your Reported-by, cc-ing -stable
> > for v5.8 and later.
> 
> I don't see the fix in Linus' master branch. Given that 8344496e8b49 was
> introduced in v5.9-rc1, shouldn't this be treated as a regression and
> merged before Linus releases v5.9 ?

The current plan is that it goes in during the upcoming merge window,
a few weeks from now.  However, it sounds like you need it sooner.
I will try doing a pull request and see what happens.

							Thanx, Paul

> > > > ------------------------------------------------------------------------
> > > > 
> > > > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> > > > index 835e2df..3dc3ffc 100644
> > > > --- a/kernel/rcu/tasks.h
> > > > +++ b/kernel/rcu/tasks.h
> > > > @@ -590,9 +590,9 @@ void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
> > > >  }
> > > >  
> > > >  #else /* #ifdef CONFIG_TASKS_RCU */
> > > > -static void show_rcu_tasks_classic_gp_kthread(void) { }
> > > > -void exit_tasks_rcu_start(void) { }
> > > > -void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
> > > > +static inline void show_rcu_tasks_classic_gp_kthread(void) { }
> > > > +static inline void exit_tasks_rcu_start(void) { }
> > > > +static inline void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
> > > >  #endif /* #else #ifdef CONFIG_TASKS_RCU */
> > > >  
> > > >  #ifdef CONFIG_TASKS_RUDE_RCU
> 
> -- 
> Regards,
> 
> Laurent Pinchart