linux-kernel - include/asm-generic/qspinlock.h:94:9: sparse: sparse: context imbalance in 'rcu_nocb_unlock'

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Message-ID: <202007241008.ngqsr0fL%lkp@intel.com>
Date:   Fri, 24 Jul 2020 10:39:14 +0800
From:   kernel test robot <lkp@...el.com>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org
Subject: include/asm-generic/qspinlock.h:94:9: sparse: sparse: context
 imbalance in 'rcu_nocb_unlock' - unexpected unlock

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   d15be546031cf65a0fc34879beca02fd90fe7ac7
commit: 5d6742b37727e111f4755155e59c5319cf5caa7b rcu/nocb: Use rcu_segcblist for no-CBs CPUs
date:   12 months ago
config: sparc64-randconfig-s031-20200723 (attached as .config)
compiler: sparc64-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
        # apt-get install sparse
        # sparse version: v0.6.2-93-g4c6cbe55-dirty
        git checkout 5d6742b37727e111f4755155e59c5319cf5caa7b
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=sparc64 

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


sparse warnings: (new ones prefixed by >>)

   kernel/rcu/tree.c:1124:13: sparse: sparse: context imbalance in 'rcu_start_this_gp' - different lock contexts for basic block
   kernel/rcu/tree.c:1520:9: sparse: sparse: context imbalance in 'rcu_gp_init' - different lock contexts for basic block
   kernel/rcu/tree.c:2226:9: sparse: sparse: context imbalance in 'force_qs_rnp' - different lock contexts for basic block
   kernel/rcu/tree.c: note: in included file (through arch/sparc/include/asm/qspinlock.h, arch/sparc/include/asm/spinlock_64.h, arch/sparc/include/asm/spinlock.h, ...):
   include/asm-generic/qspinlock.h:94:9: sparse: sparse: context imbalance in 'rcu_force_quiescent_state' - unexpected unlock
   kernel/rcu/tree.c: note: in included file:
   kernel/rcu/tree_exp.h:193:9: sparse: sparse: context imbalance in '__rcu_report_exp_rnp' - different lock contexts for basic block
   kernel/rcu/tree.c: note: in included file:
   kernel/rcu/tree_plugin.h:1503:9: sparse: sparse: context imbalance in 'rcu_nocb_lock' - wrong count at exit
   kernel/rcu/tree.c: note: in included file (through arch/sparc/include/asm/qspinlock.h, arch/sparc/include/asm/spinlock_64.h, arch/sparc/include/asm/spinlock.h, ...):
>> include/asm-generic/qspinlock.h:94:9: sparse: sparse: context imbalance in 'rcu_nocb_unlock' - unexpected unlock
   kernel/rcu/tree.c: note: in included file:
   kernel/rcu/tree_plugin.h:1530:17: sparse: sparse: context imbalance in 'rcu_nocb_unlock_irqrestore' - unexpected unlock
   kernel/rcu/tree_plugin.h:1611:13: sparse: sparse: context imbalance in '__call_rcu_nocb_wake' - wrong count at exit

vim +/rcu_nocb_unlock +94 include/asm-generic/qspinlock.h

a33fda35e3a7655 Waiman Long 2015-04-24  83  
a33fda35e3a7655 Waiman Long 2015-04-24  84  #ifndef queued_spin_unlock
a33fda35e3a7655 Waiman Long 2015-04-24  85  /**
a33fda35e3a7655 Waiman Long 2015-04-24  86   * queued_spin_unlock - release a queued spinlock
a33fda35e3a7655 Waiman Long 2015-04-24  87   * @lock : Pointer to queued spinlock structure
a33fda35e3a7655 Waiman Long 2015-04-24  88   */
a33fda35e3a7655 Waiman Long 2015-04-24  89  static __always_inline void queued_spin_unlock(struct qspinlock *lock)
a33fda35e3a7655 Waiman Long 2015-04-24  90  {
a33fda35e3a7655 Waiman Long 2015-04-24  91  	/*
ca50e426f96c905 Pan Xinhui  2016-06-03  92  	 * unlock() needs release semantics:
a33fda35e3a7655 Waiman Long 2015-04-24  93  	 */
626e5fbc1435890 Will Deacon 2018-04-26 @94  	smp_store_release(&lock->locked, 0);
a33fda35e3a7655 Waiman Long 2015-04-24  95  }
a33fda35e3a7655 Waiman Long 2015-04-24  96  #endif
a33fda35e3a7655 Waiman Long 2015-04-24  97  

:::::: The code at line 94 was first introduced by commit
:::::: 626e5fbc14358901ddaa90ce510e0fbeab310432 locking/qspinlock: Use smp_store_release() in queued_spin_unlock()

:::::: TO: Will Deacon <will.deacon@....com>
:::::: CC: Ingo Molnar <mingo@...nel.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
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