2023-05-05 11:49:51

by Wen Yang

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

From: Wen Yang <[email protected]>

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 <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Paul Menzel <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
---
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


2023-06-10 12:53:40

by tip-bot2 for Jacob Pan

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Subject: [tip: timers/core] tick/rcu: Fix bogus ratelimit condition

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

Commit-ID: 5579a8a8f15bd08b731a015630daca6ccd0f8a14
Gitweb: https://git.kernel.org/tip/5579a8a8f15bd08b731a015630daca6ccd0f8a14
Author: Wen Yang <[email protected]>
AuthorDate: Fri, 05 May 2023 00:12:53 +08:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Sat, 10 Jun 2023 14:36:17 +02:00

tick/rcu: Fix bogus ratelimit condition

The ratelimit logic in report_idle_softirq() is broken because the
exit condition is always true:

static int ratelimit;

if (ratelimit < 10)
return false; ---> always returns here

ratelimit++; ---> no chance to run

Make it check for >= 10 instead.

Fixes: 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle")
Signed-off-by: Wen Yang <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

---
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 5225467..8905505 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1030,7 +1030,7 @@ 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 */

2023-06-18 20:50:48

by tip-bot2 for Jacob Pan

[permalink] [raw]
Subject: [tip: timers/core] tick/rcu: Fix bogus ratelimit condition

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

Commit-ID: a7e282c77785c7eabf98836431b1f029481085ad
Gitweb: https://git.kernel.org/tip/a7e282c77785c7eabf98836431b1f029481085ad
Author: Wen Yang <[email protected]>
AuthorDate: Fri, 05 May 2023 00:12:53 +08:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Sun, 18 Jun 2023 22:41:53 +02:00

tick/rcu: Fix bogus ratelimit condition

The ratelimit logic in report_idle_softirq() is broken because the
exit condition is always true:

static int ratelimit;

if (ratelimit < 10)
return false; ---> always returns here

ratelimit++; ---> no chance to run

Make it check for >= 10 instead.

Fixes: 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle")
Signed-off-by: Wen Yang <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

---
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 5225467..8905505 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1030,7 +1030,7 @@ 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 */