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Message-ID: <202112141454.Emc8fZvq-lkp@intel.com>
Date: Tue, 14 Dec 2021 14:32:10 +0800
From: kernel test robot <lkp@...el.com>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
linux-kernel@...r.kernel.org
Subject: [paulmck-rcu:rcu/next 27/33] kernel/rcu/tree.c:1180:19: warning:
variable 'rnp' set but not used
tree: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next
head: a4b57ded94e522e2870ae9504f776caa0f615148
commit: ee418df93691657d27f6118d1ff8f681c52f4aa3 [27/33] rcu: Create and use a rcu_rdp_cpu_online()
config: x86_64-randconfig-c007-20211213 (https://download.01.org/0day-ci/archive/20211214/202112141454.Emc8fZvq-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project b6a2ddb6c8ac29412b1361810972e15221fa021c)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=ee418df93691657d27f6118d1ff8f681c52f4aa3
git remote add paulmck-rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
git fetch --no-tags paulmck-rcu rcu/next
git checkout ee418df93691657d27f6118d1ff8f681c52f4aa3
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/rcu/
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
All warnings (new ones prefixed by >>):
>> kernel/rcu/tree.c:1180:19: warning: variable 'rnp' set but not used [-Wunused-but-set-variable]
struct rcu_node *rnp;
^
1 warning generated.
vim +/rnp +1180 kernel/rcu/tree.c
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1163
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1164 /*
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1165 * Is the current CPU online as far as RCU is concerned?
2036d94a7b61ca kernel/rcutree.c Paul E. McKenney 2012-01-30 1166 *
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1167 * Disable preemption to avoid false positives that could otherwise
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1168 * happen due to the current CPU number being sampled, this task being
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1169 * preempted, its old CPU being taken offline, resuming on some other CPU,
49918a54e63c99 kernel/rcu/tree.c Paul E. McKenney 2018-07-07 1170 * then determining that its old CPU is now offline.
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1171 *
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1172 * Disable checking if in an NMI handler because we cannot safely
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1173 * report errors from NMI handlers anyway. In addition, it is OK to use
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1174 * RCU on an offline processor during initial boot, hence the check for
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1175 * rcu_scheduler_fully_active.
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1176 */
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1177 bool rcu_lockdep_current_cpu_online(void)
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1178 {
2036d94a7b61ca kernel/rcutree.c Paul E. McKenney 2012-01-30 1179 struct rcu_data *rdp;
2036d94a7b61ca kernel/rcutree.c Paul E. McKenney 2012-01-30 @1180 struct rcu_node *rnp;
b97d23c51c9fee kernel/rcu/tree.c Paul E. McKenney 2018-07-04 1181 bool ret = false;
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1182
5554788e1d4253 kernel/rcu/tree.c Paul E. McKenney 2018-05-15 1183 if (in_nmi() || !rcu_scheduler_fully_active)
f6f7ee9af7554e kernel/rcu/tree.c Fengguang Wu 2013-10-10 1184 return true;
ff5c4f5cad3306 kernel/rcu/tree.c Thomas Gleixner 2020-03-13 1185 preempt_disable_notrace();
da1df50d16171f kernel/rcu/tree.c Paul E. McKenney 2018-07-03 1186 rdp = this_cpu_ptr(&rcu_data);
2036d94a7b61ca kernel/rcutree.c Paul E. McKenney 2012-01-30 1187 rnp = rdp->mynode;
defd1f8a1f4efe kernel/rcu/tree.c David Woodhouse 2021-02-16 1188 /*
defd1f8a1f4efe kernel/rcu/tree.c David Woodhouse 2021-02-16 1189 * Strictly, we care here about the case where the current CPU is
defd1f8a1f4efe kernel/rcu/tree.c David Woodhouse 2021-02-16 1190 * in rcu_cpu_starting() and thus has an excuse for rdp->grpmask
defd1f8a1f4efe kernel/rcu/tree.c David Woodhouse 2021-02-16 1191 * not being up to date. So arch_spin_is_locked() might have a
defd1f8a1f4efe kernel/rcu/tree.c David Woodhouse 2021-02-16 1192 * false positive if it's held by some *other* CPU, but that's
defd1f8a1f4efe kernel/rcu/tree.c David Woodhouse 2021-02-16 1193 * OK because that just means a false *negative* on the warning.
defd1f8a1f4efe kernel/rcu/tree.c David Woodhouse 2021-02-16 1194 */
ee418df9369165 kernel/rcu/tree.c Paul E. McKenney 2021-12-10 1195 if (rcu_rdp_cpu_online(rdp) || arch_spin_is_locked(&rcu_state.ofl_lock))
b97d23c51c9fee kernel/rcu/tree.c Paul E. McKenney 2018-07-04 1196 ret = true;
ff5c4f5cad3306 kernel/rcu/tree.c Thomas Gleixner 2020-03-13 1197 preempt_enable_notrace();
b97d23c51c9fee kernel/rcu/tree.c Paul E. McKenney 2018-07-04 1198 return ret;
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1199 }
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1200 EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
c0d6d01bffdce1 kernel/rcutree.c Paul E. McKenney 2012-01-23 1201
:::::: The code at line 1180 was first introduced by commit
:::::: 2036d94a7b61ca5032ce90f2bda06afec0fe713e rcu: Rework detection of use of RCU by offline CPUs
:::::: TO: Paul E. McKenney <paul.mckenney@...aro.org>
:::::: CC: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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