From a6b2049d9f3244d697fd18f7eea2631d2e87b7bf Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 6 Oct 2021 13:18:52 +0200
Subject: [PATCH] irq_work: Also rcuwait for !IRQ_WORK_HARD_IRQ on PREEMPT_RT
References: bsc#1189998 (PREEMPT_RT prerequisite backports)
Patch-mainline: v5.16-rc1
Git-commit: 09089db79859cbccccd8df95b034f36f7027efa6
On PREEMPT_RT most items are processed as LAZY via softirq context.
Avoid to spin-wait for them because irq_work_sync() could have higher
priority and not allow the irq-work to be completed.
Wait additionally for !IRQ_WORK_HARD_IRQ irq_work items on PREEMPT_RT.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211006111852.1514359-5-bigeasy@linutronix.de
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
include/linux/irq_work.h | 5 +++++
kernel/irq_work.c | 6 ++++--
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h
index b48955e9c920..8cd11a223260 100644
--- a/include/linux/irq_work.h
+++ b/include/linux/irq_work.h
@@ -49,6 +49,11 @@ static inline bool irq_work_is_busy(struct irq_work *work)
return atomic_read(&work->node.a_flags) & IRQ_WORK_BUSY;
}
+static inline bool irq_work_is_hard(struct irq_work *work)
+{
+ return atomic_read(&work->node.a_flags) & IRQ_WORK_HARD_IRQ;
+}
+
bool irq_work_queue(struct irq_work *work);
bool irq_work_queue_on(struct irq_work *work, int cpu);
diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 90b6b56f92e9..f7df715ec28e 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -217,7 +217,8 @@ void irq_work_single(void *arg)
*/
(void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY);
- if (!arch_irq_work_has_interrupt())
+ if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
+ !arch_irq_work_has_interrupt())
rcuwait_wake_up(&work->irqwait);
}
@@ -277,7 +278,8 @@ void irq_work_sync(struct irq_work *work)
lockdep_assert_irqs_enabled();
might_sleep();
- if (!arch_irq_work_has_interrupt()) {
+ if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) ||
+ !arch_irq_work_has_interrupt()) {
rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work),
TASK_UNINTERRUPTIBLE);
return;