Merge branch 'x86/core' into cpus4096

1 files changed, 19 insertions, 0 deletions

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 88c8eb70f54a..bc8e80a86bca 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -23,10 +23,20 @@ static int trace_test_buffer_cpu(struct trace_array *tr, int cpu)
 {
         struct ring_buffer_event *event;
         struct trace_entry *entry;
+        unsigned int loops = 0;
 
         while ((event = ring_buffer_consume(tr->buffer, cpu, NULL))) {
                 entry = ring_buffer_event_data(event);
 
+                /*
+                 * The ring buffer is a size of trace_buf_size, if
+                 * we loop more than the size, there's something wrong
+                 * with the ring buffer.
+                 */
+                if (loops++ > trace_buf_size) {
+                        printk(KERN_CONT ".. bad ring buffer ");
+                        goto failed;
+                }
                 if (!trace_valid_entry(entry)) {
                         printk(KERN_CONT ".. invalid entry %d ",
                                 entry->type);
@@ -57,11 +67,20 @@ static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
 
         cnt = ring_buffer_entries(tr->buffer);
 
+        /*
+         * The trace_test_buffer_cpu runs a while loop to consume all data.
+         * If the calling tracer is broken, and is constantly filling
+         * the buffer, this will run forever, and hard lock the box.
+         * We disable the ring buffer while we do this test to prevent
+         * a hard lock up.
+         */
+        tracing_off();
         for_each_possible_cpu(cpu) {
                 ret = trace_test_buffer_cpu(tr, cpu);
                 if (ret)
                         break;
         }
+        tracing_on();
         __raw_spin_unlock(&ftrace_max_lock);
         local_irq_restore(flags);