linux-kernel - [tip: core/rcu] rcu: Fix tracepoint tracking RCU CPU kthread utilization

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Date:   Sat, 25 Jan 2020 10:42:41 -0000
From:   "tip-bot2 for Lai Jiangshan" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Lai Jiangshan <jiangshanlai@...il.com>,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: core/rcu] rcu: Fix tracepoint tracking RCU CPU kthread utilization

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     2488a5e695564897a0f8ea42cd3af71647cd26d2
Gitweb:        https://git.kernel.org/tip/2488a5e695564897a0f8ea42cd3af71647cd26d2
Author:        Lai Jiangshan <jiangshanlai@...il.com>
AuthorDate:    Tue, 15 Oct 2019 10:23:57 
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Fri, 24 Jan 2020 10:33:31 -08:00

rcu: Fix tracepoint tracking RCU CPU kthread utilization

In the call to trace_rcu_utilization() at the start of the loop in
rcu_cpu_kthread(), "rcu_wait" is incorrect, plus this trace event needs
to be hoisted above the loop to balance with either the "rcu_wait" or
"rcu_yield", depending on how the loop exits.  This commit therefore
makes these changes.

Signed-off-by: Lai Jiangshan <jiangshanlai@...il.com>
Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index dd8cfc3..ba154a3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2474,8 +2474,8 @@ static void rcu_cpu_kthread(unsigned int cpu)
 	char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work);
 	int spincnt;
 
+	trace_rcu_utilization(TPS("Start CPU kthread@..._run"));
 	for (spincnt = 0; spincnt < 10; spincnt++) {
-		trace_rcu_utilization(TPS("Start CPU kthread@..._wait"));
 		local_bh_disable();
 		*statusp = RCU_KTHREAD_RUNNING;
 		local_irq_disable();