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irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support.

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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
This commit is contained in:
Sebastian Andrzej Siewior 2021-10-06 13:18:50 +02:00 committed by Peter Zijlstra
parent da6ff09943
commit 810979682c
2 changed files with 13 additions and 0 deletions
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3
include/linux/irq_work.h
View File

@ -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:
@ -16,11 +17,13 @@
struct irq_work {
struct __call_single_node node;
void (*func)(struct irq_work *);
struct rcuwait irqwait;
};
#define __IRQ_WORK_INIT(_func, _flags) (struct irq_work){ \
.node = { .u_flags = (_flags), }, \
.func = (_func), \
.irqwait = __RCUWAIT_INITIALIZER(irqwait), \
}
#define IRQ_WORK_INIT(_func) __IRQ_WORK_INIT(_func, 0)

10
kernel/irq_work.c
View File

@ -160,6 +160,9 @@ void irq_work_single(void *arg)
* else claimed it meanwhile.
*/
(void)atomic_cmpxchg(&work->node.a_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)
@ -204,6 +207,13 @@ void irq_work_tick(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 (irq_work_is_busy(work))
cpu_relax();