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From 43a520143b091d79168ca3284aa23501c09f711e Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@kernel.org>
Date: Tue, 8 Feb 2022 17:16:35 +0100
Subject: [PATCH] lib/irq_poll: Declare IRQ_POLL softirq vector as
ksoftirqd-parking safe
The following warning may appear while setting a CPU down:
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #20!!!
The IRQ_POLL_SOFTIRQ vector can be raised during the hotplug cpu_down()
path after ksoftirqd is parked and before the CPU actually dies. However
this is handled afterward at the CPUHP_IRQ_POLL_DEAD stage where the
queue gets migrated.
Hence this warning can be considered spurious and the vector can join
the "hotplug-safe" list.
Reported-and-tested-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
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>
---
include/linux/interrupt.h | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 9613326d2f8af1..f40754caaefa43 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -580,12 +580,15 @@ enum
};
/*
- * Ignoring the RCU vector after ksoftirqd is parked is fine
- * because:
- * 1) rcutree_migrate_callbacks() takes care of the queue.
+ * The following vectors can be safely ignored after ksoftirqd is parked:
+ *
+ * _ RCU:
+ * 1) rcutree_migrate_callbacks() migrates the queue.
* 2) rcu_report_dead() reports the final quiescent states.
+ *
+ * _ IRQ_POLL: irq_poll_cpu_dead() migrates the queue
*/
-#define SOFTIRQ_HOTPLUG_SAFE_MASK (BIT(RCU_SOFTIRQ))
+#define SOFTIRQ_HOTPLUG_SAFE_MASK (BIT(RCU_SOFTIRQ) | BIT(IRQ_POLL_SOFTIRQ))
/* map softirq index to softirq name. update 'softirq_to_name' in
* kernel/softirq.c when adding a new softirq.
|