Initial import

1 files changed, 196 insertions, 0 deletions

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
new file mode 100644
index 000000000..cbf9fb899
--- /dev/null
+++ b/kernel/irq_work.c
@@ -0,0 +1,196 @@
+/*
+ * 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 <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)
+{
+	unsigned long flags, oflags, nflags;
+
+	/*
+	 * Start with our best wish as a premise but only trust any
+	 * flag value after cmpxchg() result.
+	 */
+	flags = work->flags & ~IRQ_WORK_PENDING;
+	for (;;) {
+		nflags = flags | IRQ_WORK_FLAGS;
+		oflags = cmpxchg(&work->flags, flags, nflags);
+		if (oflags == flags)
+			break;
+		if (oflags & IRQ_WORK_PENDING)
+			return false;
+		flags = oflags;
+		cpu_relax();
+	}
+
+	return true;
+}
+
+void __weak arch_irq_work_raise(void)
+{
+	/*
+	 * Lame architectures will get the timer tick callback
+	 */
+}
+
+#ifdef CONFIG_SMP
+/*
+ * 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)
+{
+	/* All work should have been flushed before going offline */
+	WARN_ON_ONCE(cpu_is_offline(cpu));
+
+	/* Arch remote IPI send/receive backend aren't NMI safe */
+	WARN_ON_ONCE(in_nmi());
+
+	/* Only queue if not already pending */
+	if (!irq_work_claim(work))
+		return false;
+
+	if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
+		arch_send_call_function_single_ipi(cpu);
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(irq_work_queue_on);
+#endif
+
+/* 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();
+
+	/* If the work is "lazy", handle it from next tick if any */
+	if (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();
+	}
+
+	preempt_enable();
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(irq_work_queue);
+
+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;
+}
+
+static void irq_work_run_list(struct llist_head *list)
+{
+	unsigned long flags;
+	struct irq_work *work;
+	struct llist_node *llnode;
+
+	BUG_ON(!irqs_disabled());
+
+	if (llist_empty(list))
+		return;
+
+	llnode = llist_del_all(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.
+		 * 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 = work->flags & ~IRQ_WORK_PENDING;
+		xchg(&work->flags, flags);
+
+		work->func(work);
+		/*
+		 * Clear the BUSY bit and return to the free state if
+		 * no-one else claimed it meanwhile.
+		 */
+		(void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
+	}
+}
+
+/*
+ * 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)
+{
+	WARN_ON_ONCE(irqs_disabled());
+
+	while (work->flags & IRQ_WORK_BUSY)
+		cpu_relax();
+}
+EXPORT_SYMBOL_GPL(irq_work_sync);