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SubjectRe: [paulmck-rcu:dev.2023.03.17a 33/38] kernel/rcu/tasks.h:140:20: warning: 'tasks_rcu_exit_srcu' defined but not used
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);
> | ^~~~~~~~~~~~~~~~~~

It is true that if you build a kernel with CONFIG_TASKS_RCU_GENERIC=y and
CONFIG_TASKS_RCU=n, you will get this warning. I am at a loss as to why
this commit would have changed that, but in any case it does need a fix.

Thank you for catching it!

Thanx, Paul

> vim +/tasks_rcu_exit_srcu +140 kernel/rcu/tasks.h
>
> 07e105158d97b4 Paul E. McKenney 2020-03-02 138
> eacd6f04a13331 Paul E. McKenney 2020-03-02 139 /* Track exiting tasks in order to allow them to be waited for. */
> eacd6f04a13331 Paul E. McKenney 2020-03-02 @140 DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
> eacd6f04a13331 Paul E. McKenney 2020-03-02 141
>
> :::::: The code at line 140 was first introduced by commit
> :::::: eacd6f04a1333187dd3e96e5635c0edce0a2e354 rcu-tasks: Move Tasks RCU to its own file
>
> :::::: TO: Paul E. McKenney <paulmck@kernel.org>
> :::::: CC: Paul E. McKenney <paulmck@kernel.org>
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests

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