linux-kernel - [PATCH] rcu-tasks: Use accurate runstart time for RCU Tasks boot-time testing

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Date:   Mon, 21 Nov 2022 23:01:50 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     paulmck@...nel.org, frederic@...nel.org, joel@...lfernandes.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] rcu-tasks: Use accurate runstart time for RCU Tasks boot-time testing

Currently, only get jiffies once as the runstart time for all RCU
Tasks testing. it's not accurate, for each RCU Tasks type test, since
corresponding type of synchronize_rcu_tasks*() be invoked, so before
each RCU Tasks test starts, we need to wait for the grace period of
the previous RCU Tasks test to end, there will be a deviation in the
start time of the RCU Tasks test.

Therefore, this commit at the start of each RCU Tasks test, re-fetch the
jiffies time as the runstart time.

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

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index b0b885e071fa..4a991311be9b 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1813,23 +1813,21 @@ static void test_rcu_tasks_callback(struct rcu_head *rhp)
 
 static void rcu_tasks_initiate_self_tests(void)
 {
-	unsigned long j = jiffies;
-
 	pr_info("Running RCU-tasks wait API self tests\n");
 #ifdef CONFIG_TASKS_RCU
-	tests[0].runstart = j;
+	tests[0].runstart = jiffies;
 	synchronize_rcu_tasks();
 	call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
 #endif
 
 #ifdef CONFIG_TASKS_RUDE_RCU
-	tests[1].runstart = j;
+	tests[1].runstart = jiffies;
 	synchronize_rcu_tasks_rude();
 	call_rcu_tasks_rude(&tests[1].rh, test_rcu_tasks_callback);
 #endif
 
 #ifdef CONFIG_TASKS_TRACE_RCU
-	tests[2].runstart = j;
+	tests[2].runstart = jiffies;
 	synchronize_rcu_tasks_trace();
 	call_rcu_tasks_trace(&tests[2].rh, test_rcu_tasks_callback);
 #endif
-- 
2.25.1