[PATCH] tick/rcu: fix an issue in the report_idle_softirq function

* [PATCH] tick/rcu: fix an issue in the report_idle_softirq function
@ 2023-05-04 16:12 wenyang.linux
  2023-06-10 12:45 ` [tip: timers/core] tick/rcu: Fix bogus ratelimit condition tip-bot2 for Wen Yang
  2023-06-18 20:49 ` tip-bot2 for Wen Yang
  0 siblings, 2 replies; 3+ messages in thread
From: wenyang.linux @ 2023-05-04 16:12 UTC (permalink / raw)
  To: Frederic Weisbecker, Thomas Gleixner, Ingo Molnar
  Cc: Wen Yang, Frederic Weisbecker, Peter Zijlstra, Paul E . McKenney,
	Paul Menzel, linux-kernel

From: Wen Yang <wenyang.linux@foxmail.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@foxmail.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.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


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