linux-kernel - [PATCH] tick/rcu: fix an issue in the report_idle

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Date:   Fri,  5 May 2023 00:12:53 +0800
From:   wenyang.linux@...mail.com
To:     Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Wen Yang <wenyang.linux@...mail.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] tick/rcu: fix an issue in the report_idle_softirq function

From: Wen Yang <wenyang.linux@...mail.com>

Commit 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle")
introduced the function report_idle_softirq, but the ratelimit logic
was broken because it is a static variable that returned before being
incremented, as follows:

	static int ratelimit;
...

	if (ratelimit < 10)
		return false;  ---> always return here
...
	ratelimit++;           ---> no chance to run

We need to adjust  the original "< 10" logic to ">= 10".

Fixes: 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle")
Signed-off-by: Wen Yang <wenyang.linux@...mail.com>
Cc: Frederic Weisbecker <frederic@...nel.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Paul Menzel <pmenzel@...gen.mpg.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org
---
 kernel/time/tick-sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index a46506f7ec6d..8891ad1d9a11 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1035,7 +1035,7 @@ static bool report_idle_softirq(void)
 			return false;
 	}
 
-	if (ratelimit < 10)
+	if (ratelimit >= 10)
 		return false;
 
 	/* On RT, softirqs handling may be waiting on some lock */
-- 
2.25.1