Re: [paulmck-rcu:dev.2023.03.17a 33/38] kernel/rcu/tasks.h:140:20: warning: 'tasks_rcu_exit_srcu' defined but not used

["Liu, Yujie" <yujie.liu@intel.com>]

On Mon, 2023-03-20 at 21:18 -0700, Paul E. McKenney wrote:
> On Tue, Mar 21, 2023 at 02:49:08AM +0000, Liu, Yujie wrote:
> > Hi Paul,
> > 
> > On Sun, 2023-03-19 at 17:33 -0700, Paul E. McKenney wrote:
> > > On Sun, Mar 19, 2023 at 03:05:43PM +0800, kernel test robot
> > > wrote:
> > > > tree:  
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
> > > >  dev.2023.03.17a
> > > > head:   19d218a4b125a4dce12eb88097a9c55f7126ce8c
> > > > commit: 61eea4556e8cf92d4c9b483110a679d2652aa451 [33/38] srcu:
> > > > Move work-scheduling fields from srcu_struct to srcu_usage
> > > > config: x86_64-kexec
> > > > (https://download.01.org/0day-ci/archive/20230319/202303191536
> > > > .XzMSyzTl-lkp@intel.com/config)
> > > > compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
> > > > reproduce (this is a W=1 build):
> > > >         #
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=61eea4556e8cf92d4c9b483110a679d2652aa451
> > > >         git remote add paulmck-rcu
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
> > > >         git fetch --no-tags paulmck-rcu dev.2023.03.17a
> > > >         git checkout 61eea4556e8cf92d4c9b483110a679d2652aa451
> > > >         # save the config file
> > > >         mkdir build_dir && cp config build_dir/.config
> > > >         make W=1 O=build_dir ARCH=x86_64 olddefconfig
> > > >         make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
> > > > kernel/
> > > > 
> > > > If you fix the issue, kindly add following tag where applicable
> > > > > Reported-by: kernel test robot <lkp@intel.com>
> > > > > Link:
> > > > > https://lore.kernel.org/oe-kbuild-all/202303191536.XzMSyzTl-lkp@intel.com/
> > > > 
> > > > All warnings (new ones prefixed by >>):
> > > > 
> > > >    In file included from include/linux/srcu.h:49,
> > > >                     from include/linux/notifier.h:16,
> > > >                     from arch/x86/include/asm/uprobes.h:13,
> > > >                     from include/linux/uprobes.h:49,
> > > >                     from include/linux/mm_types.h:16,
> > > >                     from include/linux/sched/signal.h:13,
> > > >                     from kernel/rcu/update.c:26:
> > > > > > kernel/rcu/tasks.h:140:20: warning: 'tasks_rcu_exit_srcu'
> > > > > > defined but not used [-Wunused-variable]
> > > >      140 | DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
> > > >          |                    ^~~~~~~~~~~~~~~~~~~
> > > >    include/linux/srcutree.h:184:38: note: in definition of
> > > > macro '__DEFINE_SRCU'
> > > >      184 |         is_static struct srcu_struct name
> > > > =                                                     \
> > > >          |                                      ^~~~
> > > >    kernel/rcu/tasks.h:140:1: note: in expansion of macro
> > > > 'DEFINE_STATIC_SRCU'
> > > >      140 | DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
> > > >          | ^~~~~~~~~~~~~~~~~~
> > > 
> > > Good catch, thank you!
> > > 
> > > Does the patch shown below fix this?
> > 
> > We've tested the patch and the build warning is fixed by it.
> > Thanks.
> 
> Thank you!  May I apply your Tested-by?

Sure, with pleasure.

Tested-by: Yujie Liu <yujie.liu@intel.com>

Thanks.

>                                                         Thanx, Paul
> 
> > --
> > Best Regards,
> > Yujie
> > 
> > >                                                         Thanx,
> > > Paul
> > > 
> > > -----------------------------------------------------------------
> > > -------
> > > 
> > > commit a9b8406e51603238941dbc6fa1437f8915254ebb
> > > Author: Paul E. McKenney <paulmck@kernel.org>
> > > Date:   Sun Mar 19 17:29:20 2023 -0700
> > > 
> > >     rcu-tasks: Fix warning for unused tasks_rcu_exit_srcu
> > >     
> > >     The tasks_rcu_exit_srcu variable is used only by kernels
> > > built
> > >     with CONFIG_TASKS_RCU=y, but is defined for all kernesl with
> > >     CONFIG_TASKS_RCU_GENERIC=y.  Therefore, in kernels built with
> > >     CONFIG_TASKS_RCU_GENERIC=y but CONFIG_TASKS_RCU=n, this gives
> > >     a "defined but not used" warning.
> > >     
> > >     This commit therefore moves this variable under
> > > CONFIG_TASKS_RCU
> > >     
> > >     Link:
> > > https://lore.kernel.org/oe-kbuild-all/202303191536.XzMSyzTl-lkp@intel.com/
> > >     Reported-by: kernel test robot <lkp@intel.com>
> > >     Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> > > 
> > > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> > > index baf7ec178155..85a874d4166b 100644
> > > --- a/kernel/rcu/tasks.h
> > > +++ b/kernel/rcu/tasks.h
> > > @@ -136,10 +136,10 @@ static struct rcu_tasks rt_name
> > > =                                                 \
> > >         .kname =
> > > #rt_name,                                                        
> > >       \
> > >  }
> > >  
> > > +#ifdef CONFIG_TASKS_RCU
> > >  /* Track exiting tasks in order to allow them to be waited for.
> > > */
> > >  DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
> > >  
> > > -#ifdef CONFIG_TASKS_RCU
> > >  /* Report delay in synchronize_srcu() completion in
> > > rcu_tasks_postscan(). */
> > >  static void tasks_rcu_exit_srcu_stall(struct timer_list
> > > *unused);
> > >  static DEFINE_TIMER(tasks_rcu_exit_srcu_stall_timer,
> > > tasks_rcu_exit_srcu_stall);
> > > 
> > 
>