1 files changed, 55 insertions, 0 deletions
diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
new file mode 100644
index 00000000..4689cb07
--- /dev/null
+++ b/lib/smp_processor_id.c
@@ -0,0 +1,55 @@
+/*
+ * lib/smp_processor_id.c
+ *
+ * DEBUG_PREEMPT variant of smp_processor_id().
+ */
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+#include <linux/sched.h>
+
+notrace unsigned int debug_smp_processor_id(void)
+{
+	unsigned long preempt_count = preempt_count();
+	int this_cpu = raw_smp_processor_id();
+
+	if (likely(preempt_count))
+		goto out;
+
+	if (irqs_disabled())
+		goto out;
+
+	/*
+	 * Kernel threads bound to a single CPU can safely use
+	 * smp_processor_id():
+	 */
+	if (cpumask_equal(&current->cpus_allowed, cpumask_of(this_cpu)))
+		goto out;
+
+	/*
+	 * It is valid to assume CPU-locality during early bootup:
+	 */
+	if (system_state != SYSTEM_RUNNING)
+		goto out;
+
+	/*
+	 * Avoid recursion:
+	 */
+	preempt_disable_notrace();
+
+	if (!printk_ratelimit())
+		goto out_enable;
+
+	printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] "
+			"code: %s/%d\n",
+			preempt_count() - 1, current->comm, current->pid);
+	print_symbol("caller is %s\n", (long)__builtin_return_address(0));
+	dump_stack();
+
+out_enable:
+	preempt_enable_no_resched_notrace();
+out:
+	return this_cpu;
+}
+
+EXPORT_SYMBOL(debug_smp_processor_id);
+