rcu: Add nocb_cb_kthread check to rcu_is_callbacks_kthread()

Callbacks are invoked in RCU kthreads when calbacks are offloaded
(rcu_nocbs boot parameter) or when RCU's softirq handler has been
offloaded to rcuc kthreads (use_softirq==0).  The current code allows
for the rcu_nocbs case but not the use_softirq case.  This commit adds
support for the use_softirq case.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>

1 files changed, 19 insertions, 14 deletions

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c8ba0fe17267..0483e1338c41 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1012,6 +1012,25 @@ static void rcu_cpu_kthread_setup(unsigned int cpu)
 	WRITE_ONCE(rdp->rcuc_activity, jiffies);
 }
 
+static bool rcu_is_callbacks_nocb_kthread(struct rcu_data *rdp)
+{
+#ifdef CONFIG_RCU_NOCB_CPU
+	return rdp->nocb_cb_kthread == current;
+#else
+	return false;
+#endif
+}
+
+/*
+ * Is the current CPU running the RCU-callbacks kthread?
+ * Caller must have preemption disabled.
+ */
+static bool rcu_is_callbacks_kthread(struct rcu_data *rdp)
+{
+	return rdp->rcu_cpu_kthread_task == current ||
+			rcu_is_callbacks_nocb_kthread(rdp);
+}
+
 #ifdef CONFIG_RCU_BOOST
 
 /*
@@ -1151,15 +1170,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
 	}
 }
 
-/*
- * Is the current CPU running the RCU-callbacks kthread?
- * Caller must have preemption disabled.
- */
-static bool rcu_is_callbacks_kthread(void)
-{
-	return __this_cpu_read(rcu_data.rcu_cpu_kthread_task) == current;
-}
-
 #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
 
 /*
@@ -1242,11 +1252,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 }
 
-static bool rcu_is_callbacks_kthread(void)
-{
-	return false;
-}
-
 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
 {
 }