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tick/nohz: Add BLOCK_SOFTIRQ to the hotplug safe mask

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During CPU-hotplug stress testing combined with an I/O workload, the
following message is observed:

  "NOHZ tick-stop error: local softirq work is pending, handler #10!!!"

On CPU offline, ksoftirqd is parked at CPUHP_AP_SMPBOOT_THREADS while the
CPU still takes interrupts. A block completion raised after that point
stays pending, and if the dying CPU goes idle before teardown,
report_idle_softirq() sees it, keeps the tick alive and prints the error
above.

Such pending block completions on the outgoing CPU are drained later by
blk_softirq_cpu_dead() (CPUHP_BLOCK_SOFTIRQ_DEAD), so a pending
BLOCK_SOFTIRQ is harmless here. Add it to SOFTIRQ_HOTPLUG_SAFE_MASK like
the other teardown-covered vectors.

Signed-off-by: Wang Shuaiwei <wangshuaiwei1@xiaomi.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://patch.msgid.link/20260904064506.671203-1-wangshuaiwei1@xiaomi.com
This commit is contained in:
Wang Shuaiwei 2026-09-04 14:45:06 +08:00 committed by Thomas Gleixner
parent fd73f4a665
commit a59a940ff8
1 changed files with 4 additions and 2 deletions
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6
include/linux/interrupt.h
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@ -573,9 +573,11 @@ enum
* _ IRQ_POLL: irq_poll_cpu_dead() migrates the queue
*
* _ (HR)TIMER_SOFTIRQ: (hr)timers_dead_cpu() migrates the queue
*
* _ BLOCK_SOFTIRQ: blk_softirq_cpu_dead() completes the remaining requests
*/
#define SOFTIRQ_HOTPLUG_SAFE_MASK (BIT(TIMER_SOFTIRQ) | BIT(IRQ_POLL_SOFTIRQ) |\
BIT(HRTIMER_SOFTIRQ) | BIT(RCU_SOFTIRQ))
#define SOFTIRQ_HOTPLUG_SAFE_MASK (BIT(TIMER_SOFTIRQ) | BIT(BLOCK_SOFTIRQ) |\
BIT(IRQ_POLL_SOFTIRQ) | BIT(HRTIMER_SOFTIRQ) | BIT(RCU_SOFTIRQ))
/* map softirq index to softirq name. update 'softirq_to_name' in