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authorFrederic Weisbecker <frederic@kernel.org>2022-02-08 17:16:35 +0100
committerFrederic Weisbecker <frederic@kernel.org>2022-03-07 23:53:50 +0100
commitf96272a90d9eaea9933aaab704ddbd258feb3841 (patch)
tree95dcece73d404446f2a064227b55e07de0a8501d
parent0345691b24c076655ce8f0f4bfd24cba3467ccbd (diff)
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>
-rw-r--r--include/linux/interrupt.h11
1 files changed, 7 insertions, 4 deletions
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 9613326d2f8a..f40754caaefa 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.