linux-kernel - [PATCH] rcu/nocb: Fix dump_tree hierarchy print always active

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Date:   Fri, 04 Oct 2019 19:49:10 +0000
From:   Stefan Reiter <stefan@...aker.at>
To:     rcu@...r.kernel.org
Cc:     Stefan Reiter <stefan@...aker.at>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] rcu/nocb: Fix dump_tree hierarchy print always active

Commit 18cd8c93e69e ("rcu/nocb: Print gp/cb kthread hierarchy if
dump_tree") added print statements to rcu_organize_nocb_kthreads for
debugging, but incorrectly guarded them, causing the function to always
spew out its message.

This patch fixes it by guarding both pr_alert statements with dump_tree,
while also changing the second pr_alert to a pr_cont, to print the
hierarchy in a single line (assuming that's how it was supposed to
work).

Fixes: 18cd8c93e69e ("rcu/nocb: Print gp/cb kthread hierarchy if dump_tree")
Signed-off-by: Stefan Reiter <stefan@...aker.at>
---

First time contributing to the kernel, hope I'm doing this right :)

 kernel/rcu/tree_plugin.h | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 2defc7fe74c3..7cbf4a0f3eff 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2346,15 +2346,19 @@ static void __init rcu_organize_nocb_kthreads(void)
 			nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls;
 			rdp->nocb_gp_rdp = rdp;
 			rdp_gp = rdp;
-			if (!firsttime && dump_tree)
-				pr_cont("\n");
-			firsttime = false;
-			pr_alert("%s: No-CB GP kthread CPU %d:", __func__, cpu);
+			if (dump_tree) {
+				if (!firsttime)
+					pr_cont("\n");
+				firsttime = false;
+				pr_alert("%s: No-CB GP kthread CPU %d:",
+					 __func__, cpu);
+			}
 		} else {
 			/* Another CB kthread, link to previous GP kthread. */
 			rdp->nocb_gp_rdp = rdp_gp;
 			rdp_prev->nocb_next_cb_rdp = rdp;
-			pr_alert(" %d", cpu);
+			if (dump_tree)
+				pr_cont(" %d", cpu);
 		}
 		rdp_prev = rdp;
 	}
-- 
2.23.0