1 files changed, 68 insertions, 1 deletions

diff --git a/kernel/softirq.c b/kernel/softirq.c
index d082e7840f88..7b525c904462 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -624,6 +624,24 @@ static inline void tick_irq_exit(void)
 #endif
 }
 
+#ifdef CONFIG_IRQ_FORCED_THREADING
+DEFINE_PER_CPU(struct task_struct *, ktimerd);
+DEFINE_PER_CPU(unsigned long, pending_timer_softirq);
+
+static void wake_timersd(void)
+{
+	struct task_struct *tsk = __this_cpu_read(ktimerd);
+
+	if (tsk)
+		wake_up_process(tsk);
+}
+
+#else
+
+static inline void wake_timersd(void) { }
+
+#endif
+
 static inline void __irq_exit_rcu(void)
 {
 #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
@@ -636,6 +654,10 @@ static inline void __irq_exit_rcu(void)
 	if (!in_interrupt() && local_softirq_pending())
 		invoke_softirq();
 
+	if (IS_ENABLED(CONFIG_IRQ_FORCED_THREADING) && force_irqthreads() &&
+	    local_timers_pending_force_th() && !(in_nmi() | in_hardirq()))
+		wake_timersd();
+
 	tick_irq_exit();
 }
 
@@ -971,12 +993,57 @@ static struct smp_hotplug_thread softirq_threads = {
 	.thread_comm		= "ksoftirqd/%u",
 };
 
+#ifdef CONFIG_IRQ_FORCED_THREADING
+static void ktimerd_setup(unsigned int cpu)
+{
+	/* Above SCHED_NORMAL to handle timers before regular tasks. */
+	sched_set_fifo_low(current);
+}
+
+static int ktimerd_should_run(unsigned int cpu)
+{
+	return local_timers_pending_force_th();
+}
+
+void raise_ktimers_thread(unsigned int nr)
+{
+	trace_softirq_raise(nr);
+	__this_cpu_or(pending_timer_softirq, BIT(nr));
+}
+
+static void run_ktimerd(unsigned int cpu)
+{
+	unsigned int timer_si;
+
+	ksoftirqd_run_begin();
+
+	timer_si = local_timers_pending_force_th();
+	__this_cpu_write(pending_timer_softirq, 0);
+	or_softirq_pending(timer_si);
+
+	__do_softirq();
+
+	ksoftirqd_run_end();
+}
+
+static struct smp_hotplug_thread timer_thread = {
+	.store			= &ktimerd,
+	.setup			= ktimerd_setup,
+	.thread_should_run	= ktimerd_should_run,
+	.thread_fn		= run_ktimerd,
+	.thread_comm		= "ktimers/%u",
+};
+#endif
+
 static __init int spawn_ksoftirqd(void)
 {
 	cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
 				  takeover_tasklets);
 	BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
-
+#ifdef CONFIG_IRQ_FORCED_THREADING
+	if (force_irqthreads())
+		BUG_ON(smpboot_register_percpu_thread(&timer_thread));
+#endif
 	return 0;
 }
 early_initcall(spawn_ksoftirqd);