1 files changed, 59 insertions, 0 deletions
diff --git a/arch/x86/kernel/tracepoint.c b/arch/x86/kernel/tracepoint.c
new file mode 100644
index 000000000..1c113db9e
--- /dev/null
+++ b/arch/x86/kernel/tracepoint.c
@@ -0,0 +1,59 @@
+/*
+ * Code for supporting irq vector tracepoints.
+ *
+ * Copyright (C) 2013 Seiji Aguchi <seiji.aguchi@hds.com>
+ *
+ */
+#include <asm/hw_irq.h>
+#include <asm/desc.h>
+#include <linux/atomic.h>
+
+atomic_t trace_idt_ctr = ATOMIC_INIT(0);
+struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
+				(unsigned long) trace_idt_table };
+
+/* No need to be aligned, but done to keep all IDTs defined the same way. */
+gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss;
+
+static int trace_irq_vector_refcount;
+static DEFINE_MUTEX(irq_vector_mutex);
+
+static void set_trace_idt_ctr(int val)
+{
+	atomic_set(&trace_idt_ctr, val);
+	/* Ensure the trace_idt_ctr is set before sending IPI */
+	wmb();
+}
+
+static void switch_idt(void *arg)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	load_current_idt();
+	local_irq_restore(flags);
+}
+
+void trace_irq_vector_regfunc(void)
+{
+	mutex_lock(&irq_vector_mutex);
+	if (!trace_irq_vector_refcount) {
+		set_trace_idt_ctr(1);
+		smp_call_function(switch_idt, NULL, 0);
+		switch_idt(NULL);
+	}
+	trace_irq_vector_refcount++;
+	mutex_unlock(&irq_vector_mutex);
+}
+
+void trace_irq_vector_unregfunc(void)
+{
+	mutex_lock(&irq_vector_mutex);
+	trace_irq_vector_refcount--;
+	if (!trace_irq_vector_refcount) {
+		set_trace_idt_ctr(0);
+		smp_call_function(switch_idt, NULL, 0);
+		switch_idt(NULL);
+	}
+	mutex_unlock(&irq_vector_mutex);
+}