On Fri, Mar 09, 2018 at 05:41:27AM +0800, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/dev
> head:   b8909ec707bb5beba94e7c7d62cc6b3115ceae50
> commit: b8909ec707bb5beba94e7c7d62cc6b3115ceae50 [39/39] rcu: Protect all sync_rcu_preempt_exp_done() with rcu_node lock
> reproduce:
>         # apt-get install sparse
>         git checkout b8909ec707bb5beba94e7c7d62cc6b3115ceae50
>         make ARCH=x86_64 allmodconfig
>         make C=1 CF=-D__CHECK_ENDIAN__
> 
> 
> sparse warnings: (new ones prefixed by >>)
> 
[...]
>    kernel/rcu/tree.c:345:6: sparse: symbol 'rcu_dynticks_curr_cpu_in_eqs' was not declared. Should it be static?
>    kernel/rcu/tree.c:3953:21: sparse: incorrect type in argument 1 (different modifiers) @@    expected int ( *threadfn )( ... ) @@    got int ( [noreint ( *threadfn )( ... ) @@
>    kernel/rcu/tree.c:3953:21:    expected int ( *threadfn )( ... )
>    kernel/rcu/tree.c:3953:21:    got int ( [noreturn] *<noident> )( ... )
> >> kernel/rcu/tree_exp.h:163:9: sparse: incorrect type in argument 1 (different modifiers) @@    expected struct lockdep_map const *lock @@    got strustruct lockdep_map const *lock @@
>    kernel/rcu/tree_exp.h:163:9:    expected struct lockdep_map const *lock
>    kernel/rcu/tree_exp.h:163:9:    got struct lockdep_map [noderef] *<noident>
>    kernel/rcu/tree.c:1752:9: sparse: context imbalance in 'rcu_start_future_gp' - different lock contexts for basic block
>    kernel/rcu/tree.c:2786:9: sparse: context imbalance in 'force_qs_rnp' - different lock contexts for basic block
>    kernel/rcu/tree.c:2849:25: sparse: context imbalance in 'force_quiescent_state' - unexpected unlock
>    kernel/rcu/tree_exp.h:203:9: sparse: too many warnings
> 
> vim +163 kernel/rcu/tree_exp.h
> 
>    151	
>    152	/*
>    153	 * Return non-zero if there is no RCU expedited grace period in progress
>    154	 * for the specified rcu_node structure, in other words, if all CPUs and
>    155	 * tasks covered by the specified rcu_node structure have done their bit
>    156	 * for the current expedited grace period.  Works only for preemptible
>    157	 * RCU -- other RCU implementation use other means.
>    158	 *
>    159	 * Caller must hold the specificed rcu_node structure's ->lock
>    160	 */
>    161	static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp)
>    162	{
>  > 163		lockdep_assert_held(&rnp->lock);

OK, so we need ACCESS_PRIVATE() to visit ->lock in rcu_node. I will
introduce something like:

	#define rcu_node_lock_assert_held(rnp) lockdep_assert_held(&ACCESS_PRIVATE(rnp, lock))

in v3.

Regards,
Boqun
>    164	
>    165		return rnp->exp_tasks == NULL &&
>    166		       READ_ONCE(rnp->expmask) == 0;
>    167	}
>    168	
> 
> ---
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