1 files changed, 145 insertions, 0 deletions
diff --git a/kernel/irq_work.c b/kernel/irq_work.c
new file mode 100644
index 00000000..1588e3b2
--- /dev/null
+++ b/kernel/irq_work.c
@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
+ *
+ * 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 <asm/processor.h>
+
+/*
+ * An entry can be in one of four states:
+ *
+ * free	     NULL, 0 -> {claimed}       : free to be used
+ * claimed   NULL, 3 -> {pending}       : claimed to be enqueued
+ * pending   next, 3 -> {busy}          : queued, pending callback
+ * busy      NULL, 2 -> {free, claimed} : callback in progress, can be claimed
+ */
+
+#define IRQ_WORK_PENDING	1UL
+#define IRQ_WORK_BUSY		2UL
+#define IRQ_WORK_FLAGS		3UL
+
+static DEFINE_PER_CPU(struct llist_head, irq_work_list);
+
+/*
+ * Claim the entry so that no one else will poke at it.
+ */
+static bool irq_work_claim(struct irq_work *work)
+{
+	unsigned long flags, nflags;
+
+	for (;;) {
+		flags = work->flags;
+		if (flags & IRQ_WORK_PENDING)
+			return false;
+		nflags = flags | IRQ_WORK_FLAGS;
+		if (cmpxchg(&work->flags, flags, nflags) == flags)
+			break;
+		cpu_relax();
+	}
+
+	return true;
+}
+
+void __weak arch_irq_work_raise(void)
+{
+	/*
+	 * Lame architectures will get the timer tick callback
+	 */
+}
+
+/*
+ * Queue the entry and raise the IPI if needed.
+ */
+static void __irq_work_queue(struct irq_work *work)
+{
+	bool empty;
+
+	preempt_disable();
+
+	empty = llist_add(&work->llnode, &__get_cpu_var(irq_work_list));
+	/* The list was empty, raise self-interrupt to start processing. */
+	if (empty)
+		arch_irq_work_raise();
+
+	preempt_enable();
+}
+
+/*
+ * Enqueue the irq_work @entry, returns true on success, failure when the
+ * @entry was already enqueued by someone else.
+ *
+ * Can be re-enqueued while the callback is still in progress.
+ */
+bool irq_work_queue(struct irq_work *work)
+{
+	if (!irq_work_claim(work)) {
+		/*
+		 * Already enqueued, can't do!
+		 */
+		return false;
+	}
+
+	__irq_work_queue(work);
+	return true;
+}
+EXPORT_SYMBOL_GPL(irq_work_queue);
+
+/*
+ * Run the irq_work entries on this cpu. Requires to be ran from hardirq
+ * context with local IRQs disabled.
+ */
+void irq_work_run(void)
+{
+	struct irq_work *work;
+	struct llist_head *this_list;
+	struct llist_node *llnode;
+
+	this_list = &__get_cpu_var(irq_work_list);
+	if (llist_empty(this_list))
+		return;
+
+	BUG_ON(!in_irq());
+	BUG_ON(!irqs_disabled());
+
+	llnode = llist_del_all(this_list);
+	while (llnode != NULL) {
+		work = llist_entry(llnode, struct irq_work, llnode);
+
+		llnode = llist_next(llnode);
+
+		/*
+		 * Clear the PENDING bit, after this point the @work
+		 * can be re-used.
+		 */
+		work->flags = IRQ_WORK_BUSY;
+		work->func(work);
+		/*
+		 * Clear the BUSY bit and return to the free state if
+		 * no-one else claimed it meanwhile.
+		 */
+		(void)cmpxchg(&work->flags, IRQ_WORK_BUSY, 0);
+	}
+}
+EXPORT_SYMBOL_GPL(irq_work_run);
+
+/*
+ * Synchronize against the irq_work @entry, ensures the entry is not
+ * currently in use.
+ */
+void irq_work_sync(struct irq_work *work)
+{
+	WARN_ON_ONCE(irqs_disabled());
+
+	while (work->flags & IRQ_WORK_BUSY)
+		cpu_relax();
+}
+EXPORT_SYMBOL_GPL(irq_work_sync);