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SubjectRe: [rcu:rcu/dev 39/39] kernel/rcu/tree_exp.h:163:9: sparse: incorrect type in argument 1 (different modifiers)
On Thu, Mar 08, 2018 at 04:34:43PM -0800, Paul E. McKenney wrote:
> On Fri, Mar 09, 2018 at 06:52:34AM +0800, Boqun Feng wrote:
> > 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.
>
> Or use this, which is in kernel/rcu/rcu.h:
>
> #define raw_lockdep_assert_held_rcu_node(p) \
> lockdep_assert_held(&ACCESS_PRIVATE(p, lock))
>

Good point, thank you for pointing this out ;-)

Regards,
Boqun

> Thanx, Paul
>
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