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From:   Zqiang <qiang1.zhang@intel.com>
To:     paulmck@kernel.org, frederic@kernel.org
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] rcu: Dump all rcuc kthreads status for CPUs that not report quiescent state
Date:   Wed, 13 Apr 2022 15:44:11 +0800
Message-Id: <20220413074411.2369623-1-qiang1.zhang@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

If the rcutree.use_softirq is configured, when RCU Stall event
happened, dump status of all rcuc kthreads who due to starvation
prevented grace period ends on CPUs that not report quiescent
state.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
---
 kernel/rcu/tree_stall.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index d7956c03edbd..e6ecc32cfe23 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -348,6 +348,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
 }
 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
 
+static void rcuc_kthread_dump(struct rcu_data *rdp);
 /*
  * Dump stacks of all tasks running on stalled CPUs.  First try using
  * NMIs, but fall back to manual remote stack tracing on architectures
@@ -368,6 +369,7 @@ static void rcu_dump_cpu_stacks(void)
 					pr_err("Offline CPU %d blocking current GP.\n", cpu);
 				else if (!trigger_single_cpu_backtrace(cpu))
 					dump_cpu_task(cpu);
+				rcuc_kthread_dump(per_cpu_ptr(&rcu_data, cpu));
 			}
 		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	}
@@ -471,6 +473,9 @@ static void rcuc_kthread_dump(struct rcu_data *rdp)
 	unsigned long j;
 	struct task_struct *rcuc;
 
+	if (use_softirq)
+		return;
+
 	rcuc = rdp->rcu_cpu_kthread_task;
 	if (!rcuc)
 		return;
@@ -659,9 +664,6 @@ static void print_cpu_stall(unsigned long gps)
 	rcu_check_gp_kthread_expired_fqs_timer();
 	rcu_check_gp_kthread_starvation();
 
-	if (!use_softirq)
-		rcuc_kthread_dump(rdp);
-
 	rcu_dump_cpu_stacks();
 
 	raw_spin_lock_irqsave_rcu_node(rnp, flags);
-- 
2.25.1