v4.19.13 snapshot.
diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
new file mode 100644
index 0000000..85925aa
--- /dev/null
+++ b/lib/smp_processor_id.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * lib/smp_processor_id.c
+ *
+ * DEBUG_PREEMPT variant of smp_processor_id().
+ */
+#include <linux/export.h>
+#include <linux/sched.h>
+
+notrace static unsigned int check_preemption_disabled(const char *what1,
+ const char *what2)
+{
+ 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(¤t->cpus_allowed, cpumask_of(this_cpu)))
+ goto out;
+
+ /*
+ * It is valid to assume CPU-locality during early bootup:
+ */
+ if (system_state < SYSTEM_SCHEDULING)
+ goto out;
+
+ /*
+ * Avoid recursion:
+ */
+ preempt_disable_notrace();
+
+ if (!printk_ratelimit())
+ goto out_enable;
+
+ printk(KERN_ERR "BUG: using %s%s() in preemptible [%08x] code: %s/%d\n",
+ what1, what2, preempt_count() - 1, current->comm, current->pid);
+
+ printk("caller is %pS\n", __builtin_return_address(0));
+ dump_stack();
+
+out_enable:
+ preempt_enable_no_resched_notrace();
+out:
+ return this_cpu;
+}
+
+notrace unsigned int debug_smp_processor_id(void)
+{
+ return check_preemption_disabled("smp_processor_id", "");
+}
+EXPORT_SYMBOL(debug_smp_processor_id);
+
+notrace void __this_cpu_preempt_check(const char *op)
+{
+ check_preemption_disabled("__this_cpu_", op);
+}
+EXPORT_SYMBOL(__this_cpu_preempt_check);