linux-kernel - RE: [PATCH] rcu: Fix incorrect judgment condition in show_rcu_nocb

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Message-ID: <PH0PR11MB5880D97F865580DFB6F12A9DDADC9@PH0PR11MB5880.namprd11.prod.outlook.com>
Date:   Tue, 31 May 2022 11:24:55 +0000
From:   "Zhang, Qiang1" <qiang1.zhang@...el.com>
To:     "Zhang, Qiang1" <qiang1.zhang@...el.com>,
        "paulmck@...nel.org" <paulmck@...nel.org>,
        "frederic@...nel.org" <frederic@...nel.org>
CC:     "rcu@...r.kernel.org" <rcu@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] rcu: Fix incorrect judgment condition in
 show_rcu_nocb_state()

Hi  Frederic

Friendly ping.

Thanks
Zqiang


When check the 'rdp->nocb_cb_kthread' tasks exists, if is true, however
the output is the cpu where 'rdp->nocb_gp_kthread' is located. this
ensure that the tasks in the judgment condition and the tasks of the
cpu where the output tasks are located are the same tasks.

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 kernel/rcu/tree_nocb.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index fa8e4f82e60c..f4ee81d119c8 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -1438,8 +1438,8 @@ static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
 		(long)rdp->nocb_gp_seq,
 		rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
 		rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
-		rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
-		show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
+		rdp->nocb_gp_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+		show_rcu_should_be_on_cpu(rdp->nocb_gp_kthread));
 }
 
 /* Dump out nocb kthread state for the specified rcu_data structure. */
@@ -1483,7 +1483,7 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
 		".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
 		rcu_segcblist_n_cbs(&rdp->cblist),
 		rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
-		rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+		rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_cb_kthread) : -1,
 		show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
 
 	/* It is OK for GP kthreads to have GP state. */
-- 
2.25.1