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 000000000000..42c08ef828c5
--- /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>
+
+unsigned int debug_smp_processor_id(void)
+{
+        unsigned long preempt_count = preempt_count();
+        int this_cpu = raw_smp_processor_id();
+        cpumask_t this_mask;
+
+        if (likely(preempt_count))
+                goto out;
+
+        if (irqs_disabled())
+                goto out;
+
+        /*
+         * Kernel threads bound to a single CPU can safely use
+         * smp_processor_id():
+         */
+        this_mask = cpumask_of_cpu(this_cpu);
+
+        if (cpus_equal(current->cpus_allowed, this_mask))
+                goto out;
+
+        /*
+         * It is valid to assume CPU-locality during early bootup:
+         */
+        if (system_state != SYSTEM_RUNNING)
+                goto out;
+
+        /*
+         * Avoid recursion:
+         */
+        preempt_disable();
+
+        if (!printk_ratelimit())
+                goto out_enable;
+
+        printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] code: %s/%d\n", preempt_count(), current->comm, current->pid);
+        print_symbol("caller is %s\n", (long)__builtin_return_address(0));
+        dump_stack();
+
+out_enable:
+        preempt_enable_no_resched();
+out:
+        return this_cpu;
+}
+
+EXPORT_SYMBOL(debug_smp_processor_id);
+