[linux-next:master 4055/10701] kernel/rcu/tree_stall.h:208:19: warning: variable 'rnp' set but not used

[linux-next:master 4055/10701] kernel/rcu/tree_stall.h:208:19: warning: variable 'rnp' set but not used

[kbuild test robot]

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   fb57b1fabcb28f358901b2df90abd2b48abc1ca8
commit: 5bef8da66a9c45d3c371d74463894f1fc31dfdda [4055/10701] rcu: Add per-task state to RCU CPU stall warnings
config: nios2-randconfig-r021-20200519 (attached as .config)
compiler: nios2-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 5bef8da66a9c45d3c371d74463894f1fc31dfdda
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=nios2 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

In file included from kernel/rcu/tree.c:4075:
kernel/rcu/tree_stall.h: In function 'check_slow_task':
>> kernel/rcu/tree_stall.h:208:19: warning: variable 'rnp' set but not used [-Wunused-but-set-variable]
208 |  struct rcu_node *rnp;
|                   ^~~

vim +/rnp +208 kernel/rcu/tree_stall.h

   201	
   202	/*
   203	 * Report out the state of a not-running task that is stalling the
   204	 * current RCU grace period.
   205	 */
   206	static bool check_slow_task(struct task_struct *t, void *arg)
   207	{
 > 208		struct rcu_node *rnp;
   209		struct rcu_stall_chk_rdr *rscrp = arg;
   210	
   211		if (task_curr(t))
   212			return false; // It is running, so decline to inspect it.
   213		rscrp->nesting = t->rcu_read_lock_nesting;
   214		rscrp->rs = t->rcu_read_unlock_special;
   215		rnp = t->rcu_blocked_node;
   216		rscrp->on_blkd_list = !list_empty(&t->rcu_node_entry);
   217		return true;
   218	}
   219	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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Re: [linux-next:master 4055/10701] kernel/rcu/tree_stall.h:208:19: warning: variable 'rnp' set but not used

[Paul E. McKenney]

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On Wed, May 20, 2020 at 04:49:01AM +0800, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   fb57b1fabcb28f358901b2df90abd2b48abc1ca8
> commit: 5bef8da66a9c45d3c371d74463894f1fc31dfdda [4055/10701] rcu: Add per-task state to RCU CPU stall warnings
> config: nios2-randconfig-r021-20200519 (attached as .config)
> compiler: nios2-linux-gcc (GCC) 9.3.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         git checkout 5bef8da66a9c45d3c371d74463894f1fc31dfdda
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=nios2 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kbuild test robot <lkp@intel.com>

Good catch, fixed with your Reported-by.

							Thanx, Paul

> All warnings (new ones prefixed by >>, old ones prefixed by <<):
> 
> In file included from kernel/rcu/tree.c:4075:
> kernel/rcu/tree_stall.h: In function 'check_slow_task':
> >> kernel/rcu/tree_stall.h:208:19: warning: variable 'rnp' set but not used [-Wunused-but-set-variable]
> 208 |  struct rcu_node *rnp;
> |                   ^~~
> 
> vim +/rnp +208 kernel/rcu/tree_stall.h
> 
>    201	
>    202	/*
>    203	 * Report out the state of a not-running task that is stalling the
>    204	 * current RCU grace period.
>    205	 */
>    206	static bool check_slow_task(struct task_struct *t, void *arg)
>    207	{
>  > 208		struct rcu_node *rnp;
>    209		struct rcu_stall_chk_rdr *rscrp = arg;
>    210	
>    211		if (task_curr(t))
>    212			return false; // It is running, so decline to inspect it.
>    213		rscrp->nesting = t->rcu_read_lock_nesting;
>    214		rscrp->rs = t->rcu_read_unlock_special;
>    215		rnp = t->rcu_blocked_node;
>    216		rscrp->on_blkd_list = !list_empty(&t->rcu_node_entry);
>    217		return true;
>    218	}
>    219	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org