From 810979682ccc98dbd83f341c18a2e556c30a7164 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 6 Oct 2021 13:18:50 +0200 Subject: irq_work: Allow irq_work_sync() to sleep if irq_work() no IRQ support. 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 Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20211006111852.1514359-3-bigeasy@linutronix.de --- kernel/irq_work.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'kernel/irq_work.c') diff --git a/kernel/irq_work.c b/kernel/irq_work.c index db8c248ebc8c..e789beda8297 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -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(); -- cgit v1.2.3