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From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
	mingo@kernel.org, jiangshanlai@gmail.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 1/4] rcu: Mark obtuse portion of stall warning as internal debug
Date: Wed,  6 Jan 2021 08:52:28 -0800
Message-ID: <20210106165231.20441-1-paulmck@kernel.org> (raw)
In-Reply-To: <20210106165210.GA20296@paulmck-ThinkPad-P72>

From: "Paul E. McKenney" <paulmck@kernel.org>

There is a rather obtuse string that can be printed as part of an
expedited RCU CPU stall-warning message that starts with "blocking
rcu_node structures".  Under normal conditions, most of this message
is just repeating the list of CPUs blocking the current expedited grace
period, but in a manner that is rather difficult to read.  This commit
therefore marks this message as "(internal RCU debug)" in an effort to
give people the option of avoiding wasting time attempting to extract
nonexistent additional meaning from this portion of the message.

Reported-by: Jonathan Lemon <bsd@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree_exp.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 8760b6e..6c6ff06 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -545,7 +545,7 @@ static void synchronize_rcu_expedited_wait(void)
 			data_race(rnp_root->expmask),
 			".T"[!!data_race(rnp_root->exp_tasks)]);
 		if (ndetected) {
-			pr_err("blocking rcu_node structures:");
+			pr_err("blocking rcu_node structures (internal RCU debug):");
 			rcu_for_each_node_breadth_first(rnp) {
 				if (rnp == rnp_root)
 					continue; /* printed unconditionally */
-- 
2.9.5


  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-06 16:52 [PATCH tip/core/rcu 0/4] Stall-warning updates for v5.12 Paul E. McKenney
2021-01-06 16:52 ` paulmck [this message]
2021-01-06 16:52 ` [PATCH tip/core/rcu 2/4] rcu: For RCU grace-period kthread starvation, dump last CPU it ran on paulmck
2021-01-06 16:52 ` [PATCH tip/core/rcu 3/4] rcu: Do not NMI offline CPUs paulmck
2021-01-06 16:52 ` [PATCH tip/core/rcu 4/4] rcu: Check and report missed fqs timer wakeup on RCU stall paulmck

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