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@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20211006111852.1514359-3-bigeasy@xxxxxxxxxxxxx --- 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(); -- 2.34.0
