From 9420fb934cf15bee1cb6999676fa2dbd2560efc2 Mon Sep 17 00:00:00 2001 From: Zqiang Date: Mon, 21 Nov 2022 23:01:50 +0800 Subject: [PATCH] rcu-tasks: Use accurate runstart time for RCU Tasks boot-time testing Currently, test_rcu_tasks_callback() reads from the jiffies counter only once when this function is invoked. This introduces inaccuracies because of the latencies induced by the synchronize_rcu_tasks*() invocations. This commit therefore re-reads the jiffies counter at the beginning of each test, thus avoiding penalizing later tests for the latencies induced by earlier tests. Therefore, this commit at the start of each RCU Tasks test, re-fetch the jiffies time as the runstart time. Signed-off-by: Zqiang Signed-off-by: Paul E. McKenney --- 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 fe9840d..c418aa1 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -1815,23 +1815,21 @@ 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 -- 2.7.4