rcu: Allow processing deferred QSes for exiting RCU-preempt readers

If an RCU-preempt read-side critical section is exiting, that is,
->rcu_read_lock_nesting is negative, then it is a good time to look
at the possibility of reporting deferred quiescent states.  This
commit therefore updates the checks in rcu_preempt_need_deferred_qs()
to allow exiting critical sections to report deferred quiescent states.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 5427913..24c2096 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -602,7 +602,7 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
 {
        return (this_cpu_ptr(&rcu_preempt_data)->deferred_qs ||
                READ_ONCE(t->rcu_read_unlock_special.s)) &&
-              !t->rcu_read_lock_nesting;
+              t->rcu_read_lock_nesting <= 0;
 }
 
 /*