1 files changed, 204 insertions, 0 deletions
diff --git a/kernel/irq_work.c b/kernel/irq_work.c
new file mode 100644
index 000000000..eca83965b
--- /dev/null
+++ b/kernel/irq_work.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra
+ *
+ * Provides a framework for enqueueing and running callbacks from hardirq
+ * context. The enqueueing is NMI-safe.
+ */
+
+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/irq_work.h>
+#include <linux/percpu.h>
+#include <linux/hardirq.h>
+#include <linux/irqflags.h>
+#include <linux/sched.h>
+#include <linux/tick.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
+#include <linux/smp.h>
+#include <asm/processor.h>
+
+
+static DEFINE_PER_CPU(struct llist_head, raised_list);
+static DEFINE_PER_CPU(struct llist_head, lazy_list);
+
+/*
+ * Claim the entry so that no one else will poke at it.
+ */
+static bool irq_work_claim(struct irq_work *work)
+{
+	int oflags;
+
+	oflags = atomic_fetch_or(IRQ_WORK_CLAIMED | CSD_TYPE_IRQ_WORK, &work->flags);
+	/*
+	 * If the work is already pending, no need to raise the IPI.
+	 * The pairing atomic_fetch_andnot() in irq_work_run() makes sure
+	 * everything we did before is visible.
+	 */
+	if (oflags & IRQ_WORK_PENDING)
+		return false;
+	return true;
+}
+
+void __weak arch_irq_work_raise(void)
+{
+	/*
+	 * Lame architectures will get the timer tick callback
+	 */
+}
+
+/* Enqueue on current CPU, work must already be claimed and preempt disabled */
+static void __irq_work_queue_local(struct irq_work *work)
+{
+	/* If the work is "lazy", handle it from next tick if any */
+	if (atomic_read(&work->flags) & IRQ_WORK_LAZY) {
+		if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
+		    tick_nohz_tick_stopped())
+			arch_irq_work_raise();
+	} else {
+		if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
+			arch_irq_work_raise();
+	}
+}
+
+/* Enqueue the irq work @work on the current CPU */
+bool irq_work_queue(struct irq_work *work)
+{
+	/* Only queue if not already pending */
+	if (!irq_work_claim(work))
+		return false;
+
+	/* Queue the entry and raise the IPI if needed. */
+	preempt_disable();
+	__irq_work_queue_local(work);
+	preempt_enable();
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(irq_work_queue);
+
+/*
+ * Enqueue the irq_work @work on @cpu unless it's already pending
+ * somewhere.
+ *
+ * Can be re-enqueued while the callback is still in progress.
+ */
+bool irq_work_queue_on(struct irq_work *work, int cpu)
+{
+#ifndef CONFIG_SMP
+	return irq_work_queue(work);
+
+#else /* CONFIG_SMP: */
+	/* All work should have been flushed before going offline */
+	WARN_ON_ONCE(cpu_is_offline(cpu));
+
+	/* Only queue if not already pending */
+	if (!irq_work_claim(work))
+		return false;
+
+	preempt_disable();
+	if (cpu != smp_processor_id()) {
+		/* Arch remote IPI send/receive backend aren't NMI safe */
+		WARN_ON_ONCE(in_nmi());
+		__smp_call_single_queue(cpu, &work->llnode);
+	} else {
+		__irq_work_queue_local(work);
+	}
+	preempt_enable();
+
+	return true;
+#endif /* CONFIG_SMP */
+}
+
+
+bool irq_work_needs_cpu(void)
+{
+	struct llist_head *raised, *lazy;
+
+	raised = this_cpu_ptr(&raised_list);
+	lazy = this_cpu_ptr(&lazy_list);
+
+	if (llist_empty(raised) || arch_irq_work_has_interrupt())
+		if (llist_empty(lazy))
+			return false;
+
+	/* All work should have been flushed before going offline */
+	WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
+
+	return true;
+}
+
+void irq_work_single(void *arg)
+{
+	struct irq_work *work = arg;
+	int flags;
+
+	/*
+	 * Clear the PENDING bit, after this point the @work
+	 * can be re-used.
+	 * Make it immediately visible so that other CPUs trying
+	 * to claim that work don't rely on us to handle their data
+	 * while we are in the middle of the func.
+	 */
+	flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags);
+
+	lockdep_irq_work_enter(work);
+	work->func(work);
+	lockdep_irq_work_exit(work);
+	/*
+	 * Clear the BUSY bit and return to the free state if
+	 * no-one else claimed it meanwhile.
+	 */
+	flags &= ~IRQ_WORK_PENDING;
+	(void)atomic_cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
+}
+
+static void irq_work_run_list(struct llist_head *list)
+{
+	struct irq_work *work, *tmp;
+	struct llist_node *llnode;
+
+	BUG_ON(!irqs_disabled());
+
+	if (llist_empty(list))
+		return;
+
+	llnode = llist_del_all(list);
+	llist_for_each_entry_safe(work, tmp, llnode, llnode)
+		irq_work_single(work);
+}
+
+/*
+ * hotplug calls this through:
+ *  hotplug_cfd() -> flush_smp_call_function_queue()
+ */
+void irq_work_run(void)
+{
+	irq_work_run_list(this_cpu_ptr(&raised_list));
+	irq_work_run_list(this_cpu_ptr(&lazy_list));
+}
+EXPORT_SYMBOL_GPL(irq_work_run);
+
+void irq_work_tick(void)
+{
+	struct llist_head *raised = this_cpu_ptr(&raised_list);
+
+	if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
+		irq_work_run_list(raised);
+	irq_work_run_list(this_cpu_ptr(&lazy_list));
+}
+
+/*
+ * Synchronize against the irq_work @entry, ensures the entry is not
+ * currently in use.
+ */
+void irq_work_sync(struct irq_work *work)
+{
+	lockdep_assert_irqs_enabled();
+
+	while (atomic_read(&work->flags) & IRQ_WORK_BUSY)
+		cpu_relax();
+}
+EXPORT_SYMBOL_GPL(irq_work_sync);