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From a906df425c7fd4b1e1b3e0c9112cc71b528db166 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 24 Nov 2021 17:12:19 +0100
Subject: [PATCH 307/323] irq_work: Allow irq_work_sync() to sleep if
irq_work() no IRQ support.
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.215-rt107.tar.xz
irq_work() triggers instantly an interrupt if supported by the
architecture. Otherwise the work will be processed on the next timer
tick. In worst case irq_work_sync() could spin up to a jiffy.
irq_work_sync() is usually used in tear down context which is fully
preemptible. Based on review irq_work_sync() is invoked from preemptible
context and there is one waiter at a time. This qualifies it to use
rcuwait for synchronisation.
Let irq_work_sync() synchronize with rcuwait if the architecture
processes irqwork via the timer tick.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211006111852.1514359-3-bigeasy@linutronix.de
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
include/linux/irq_work.h | 10 +++++++++-
kernel/irq_work.c | 10 ++++++++++
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h
index f941f2d7d71ce..3c6d3a96bca0f 100644
--- a/include/linux/irq_work.h
+++ b/include/linux/irq_work.h
@@ -3,6 +3,7 @@
#define _LINUX_IRQ_WORK_H
#include <linux/smp_types.h>
+#include <linux/rcuwait.h>
/*
* An entry can be in one of four states:
@@ -22,6 +23,7 @@ struct irq_work {
};
};
void (*func)(struct irq_work *);
+ struct rcuwait irqwait;
};
static inline
@@ -29,13 +31,19 @@ void init_irq_work(struct irq_work *work, void (*func)(struct irq_work *))
{
atomic_set(&work->flags, 0);
work->func = func;
+ rcuwait_init(&work->irqwait);
}
#define DEFINE_IRQ_WORK(name, _f) struct irq_work name = { \
.flags = ATOMIC_INIT(0), \
- .func = (_f) \
+ .func = (_f), \
+ .irqwait = __RCUWAIT_INITIALIZER(irqwait), \
}
+static inline bool irq_work_is_busy(struct irq_work *work)
+{
+ return atomic_read(&work->flags) & IRQ_WORK_BUSY;
+}
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 8183d30e1bb1c..8969aff790e21 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -165,6 +165,9 @@ void irq_work_single(void *arg)
*/
flags &= ~IRQ_WORK_PENDING;
(void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
+
+ if (!arch_irq_work_has_interrupt())
+ rcuwait_wake_up(&work->irqwait);
}
static void irq_work_run_list(struct llist_head *list)
@@ -231,6 +234,13 @@ void irq_work_tick_soft(void)
void irq_work_sync(struct irq_work *work)
{
lockdep_assert_irqs_enabled();
+ might_sleep();
+
+ if (!arch_irq_work_has_interrupt()) {
+ rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work),
+ TASK_UNINTERRUPTIBLE);
+ return;
+ }
while (atomic_read(&work->flags) & IRQ_WORK_BUSY)
cpu_relax();
--
2.44.0
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