[rcu:dev.2021.01.26a 61/65] kernel/rcu/tree_plugin.h:2430:9: sparse: sparse: context imbalance in 'rcu_nocb_rdp_deoffload' - wrong count at exit

[kernel test robot <lkp@intel.com>]

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CC: kbuild-all(a)lists.01.org
CC: linux-kernel(a)vger.kernel.org
TO: Frederic Weisbecker <frederic@kernel.org>
CC: "Paul E. McKenney" <paulmck@kernel.org>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2021.01.26a
head:   142d159f544763140e0f498936bca8f71563e0e0
commit: 4fbfeec81533e6ea9811e57cc848ee30522c0517 [61/65] rcu/nocb: Forbid NOCB toggling on offline CPUs
:::::: branch date: 5 days ago
:::::: commit date: 5 days ago
config: sparc64-randconfig-s031-20210202 (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: v0.6.3-215-g0fb77bb6-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=4fbfeec81533e6ea9811e57cc848ee30522c0517
        git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
        git fetch --no-tags rcu dev.2021.01.26a
        git checkout 4fbfeec81533e6ea9811e57cc848ee30522c0517
        # 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@intel.com>


"sparse warnings: (new ones prefixed by >>)"
   kernel/rcu/tree.c: note: in included file:
   kernel/rcu/tree_plugin.h:1557:5: sparse: sparse: symbol 'nocb_nobypass_lim_per_jiffy' was not declared. Should it be static?
   kernel/rcu/tree.c:1455:9: sparse: sparse: context imbalance in 'rcu_start_this_gp' - different lock contexts for basic block
   kernel/rcu/tree.c:1867:9: sparse: sparse: context imbalance in 'rcu_gp_init' - different lock contexts for basic block
   kernel/rcu/tree.c:2646:9: sparse: sparse: context imbalance in 'force_qs_rnp' - different lock contexts for basic block
   kernel/rcu/tree.c:2699:25: sparse: sparse: context imbalance in 'rcu_force_quiescent_state' - unexpected unlock
   kernel/rcu/tree.c:2729:30: sparse: sparse: context imbalance in 'rcu_core' - different lock contexts for basic block
   kernel/rcu/tree.c: note: in included file:
   kernel/rcu/tree_stall.h:316:12: sparse: sparse: context imbalance in 'rcu_print_task_stall' - unexpected unlock
   kernel/rcu/tree_stall.h:540:9: sparse: sparse: context imbalance in 'print_other_cpu_stall' - different lock contexts for basic block
   kernel/rcu/tree.c: note: in included file:
   kernel/rcu/tree_exp.h:189:9: 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:1603:16: sparse: sparse: context imbalance in 'rcu_nocb_bypass_trylock' - wrong count at exit
   kernel/rcu/tree_plugin.h:1620:13: sparse: sparse: context imbalance in 'rcu_nocb_lock' - wrong count at exit
   kernel/rcu/tree_plugin.h:1636:17: sparse: sparse: context imbalance in 'rcu_nocb_unlock' - unexpected unlock
   kernel/rcu/tree_plugin.h:1649:17: sparse: sparse: context imbalance in 'rcu_nocb_unlock_irqrestore' - unexpected unlock
   kernel/rcu/tree_plugin.h:1695:13: sparse: sparse: context imbalance in 'wake_nocb_gp' - wrong count at exit
   kernel/rcu/tree_plugin.h:1763:9: sparse: sparse: context imbalance in 'rcu_nocb_do_flush_bypass' - unexpected unlock
   kernel/rcu/tree_plugin.h:1778:13: sparse: sparse: context imbalance in 'rcu_nocb_flush_bypass' - wrong count at exit
   kernel/rcu/tree_plugin.h:1929:13: sparse: sparse: context imbalance in '__call_rcu_nocb_wake' - wrong count at exit
   kernel/rcu/tree_plugin.h:1993:9: sparse: sparse: context imbalance in 'do_nocb_bypass_wakeup_timer' - different lock contexts for basic block
   kernel/rcu/tree_plugin.h:2069:9: sparse: sparse: context imbalance in 'nocb_gp_wait' - different lock contexts for basic block
   kernel/rcu/tree_plugin.h:2287:9: sparse: sparse: context imbalance in 'nocb_cb_wait' - wrong count at exit
   kernel/rcu/tree_plugin.h:2324:13: sparse: sparse: context imbalance in 'do_nocb_deferred_wakeup_common' - different lock contexts for basic block
   kernel/rcu/tree_plugin.h:2398:9: sparse: sparse: context imbalance in 'rdp_offload_toggle' - wrong count at exit
>> kernel/rcu/tree_plugin.h:2430:9: sparse: sparse: context imbalance in 'rcu_nocb_rdp_deoffload' - wrong count at exit

vim +/rcu_nocb_rdp_deoffload +2430 kernel/rcu/tree_plugin.h

254e11efde66ca Frederic Weisbecker 2020-11-13  2400  
4fbfeec81533e6 Frederic Weisbecker 2021-01-28  2401  static long rcu_nocb_rdp_deoffload(void *arg)
254e11efde66ca Frederic Weisbecker 2020-11-13  2402  {
4fbfeec81533e6 Frederic Weisbecker 2021-01-28  2403  	struct rcu_data *rdp = arg;
254e11efde66ca Frederic Weisbecker 2020-11-13  2404  	struct rcu_segcblist *cblist = &rdp->cblist;
254e11efde66ca Frederic Weisbecker 2020-11-13  2405  	unsigned long flags;
254e11efde66ca Frederic Weisbecker 2020-11-13  2406  	int ret;
254e11efde66ca Frederic Weisbecker 2020-11-13  2407  
4fbfeec81533e6 Frederic Weisbecker 2021-01-28  2408  	WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id());
4fbfeec81533e6 Frederic Weisbecker 2021-01-28  2409  
f759081e8f5ac6 Paul E. McKenney    2020-12-21  2410  	pr_info("De-offloading %d\n", rdp->cpu);
254e11efde66ca Frederic Weisbecker 2020-11-13  2411  
254e11efde66ca Frederic Weisbecker 2020-11-13  2412  	rcu_nocb_lock_irqsave(rdp, flags);
254e11efde66ca Frederic Weisbecker 2020-11-13  2413  
254e11efde66ca Frederic Weisbecker 2020-11-13  2414  	ret = rdp_offload_toggle(rdp, false, flags);
5bb39dc956f3d4 Frederic Weisbecker 2020-11-13  2415  	swait_event_exclusive(rdp->nocb_state_wq,
5bb39dc956f3d4 Frederic Weisbecker 2020-11-13  2416  			      !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
5bb39dc956f3d4 Frederic Weisbecker 2020-11-13  2417  							SEGCBLIST_KTHREAD_GP));
69cdea873cde26 Frederic Weisbecker 2020-11-13  2418  	rcu_nocb_lock_irqsave(rdp, flags);
314202f84ddd61 Frederic Weisbecker 2020-11-13  2419  	/* Make sure nocb timer won't stay around */
69cdea873cde26 Frederic Weisbecker 2020-11-13  2420  	WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_OFF);
69cdea873cde26 Frederic Weisbecker 2020-11-13  2421  	rcu_nocb_unlock_irqrestore(rdp, flags);
69cdea873cde26 Frederic Weisbecker 2020-11-13  2422  	del_timer_sync(&rdp->nocb_timer);
69cdea873cde26 Frederic Weisbecker 2020-11-13  2423  
314202f84ddd61 Frederic Weisbecker 2020-11-13  2424  	/*
314202f84ddd61 Frederic Weisbecker 2020-11-13  2425  	 * Flush bypass. While IRQs are disabled and once we set
314202f84ddd61 Frederic Weisbecker 2020-11-13  2426  	 * SEGCBLIST_SOFTIRQ_ONLY, no callback is supposed to be
314202f84ddd61 Frederic Weisbecker 2020-11-13  2427  	 * enqueued on bypass.
314202f84ddd61 Frederic Weisbecker 2020-11-13  2428  	 */
314202f84ddd61 Frederic Weisbecker 2020-11-13  2429  	rcu_nocb_lock_irqsave(rdp, flags);
314202f84ddd61 Frederic Weisbecker 2020-11-13 @2430  	rcu_nocb_flush_bypass(rdp, NULL, jiffies);
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2431  	rcu_segcblist_set_flags(cblist, SEGCBLIST_SOFTIRQ_ONLY);
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2432  	/*
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2433  	 * With SEGCBLIST_SOFTIRQ_ONLY, we can't use
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2434  	 * rcu_nocb_unlock_irqrestore() anymore. Theoretically we
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2435  	 * could set SEGCBLIST_SOFTIRQ_ONLY with cb unlocked and IRQs
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2436  	 * disabled now, but let's be paranoid.
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2437  	 */
b9ced9e1ab51ed Frederic Weisbecker 2020-11-13  2438  	raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
314202f84ddd61 Frederic Weisbecker 2020-11-13  2439  
254e11efde66ca Frederic Weisbecker 2020-11-13  2440  	return ret;
d97b078182406c Frederic Weisbecker 2020-11-13  2441  }
d97b078182406c Frederic Weisbecker 2020-11-13  2442  

:::::: The code at line 2430 was first introduced by commit
:::::: 314202f84ddd61e4d7576ef62570ad2e2d9db06b rcu/nocb: Flush bypass before setting SEGCBLIST_SOFTIRQ_ONLY

:::::: TO: Frederic Weisbecker <frederic@kernel.org>
:::::: CC: Paul E. McKenney <paulmck@kernel.org>

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

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