Merge git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable

[sfrench/cifs-2.6.git] / kernel / trace / trace_selftest.c

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 88c8eb70f54aeb3508dda9c668f082b9a43b0c78..bc8e80a86bca4c0cf730fcf6b7bc568f2808f7e7 100644 (file)
--- 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);