tracing/function-graph-tracer: prevent hangs during self-tests

[safe/jmp/linux-2.6] / kernel / trace / trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e3dfefe..e6fac0f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4018,11 +4018,12 @@ trace_printk_seq(struct trace_seq *s)
        trace_seq_init(s);
 }
 
-void ftrace_dump(void)
+static void __ftrace_dump(bool disable_tracing)
 {
        static DEFINE_SPINLOCK(ftrace_dump_lock);
        /* use static because iter can be a bit big for the stack */
        static struct trace_iterator iter;
+       unsigned int old_userobj;
        static int dump_ran;
        unsigned long flags;
        int cnt = 0, cpu;
@@ -4034,14 +4035,17 @@ void ftrace_dump(void)
 
        dump_ran = 1;
 
-       /* No turning back! */
        tracing_off();
-       ftrace_kill();
+
+       if (disable_tracing)
+               ftrace_kill();
 
        for_each_tracing_cpu(cpu) {
                atomic_inc(&global_trace.data[cpu]->disabled);
        }
 
+       old_userobj = trace_flags & TRACE_ITER_SYM_USEROBJ;
+
        /* don't look at user memory in panic mode */
        trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
 
@@ -4086,10 +4090,26 @@ void ftrace_dump(void)
        else
                printk(KERN_TRACE "---------------------------------\n");
 
+       /* Re-enable tracing if requested */
+       if (!disable_tracing) {
+               trace_flags |= old_userobj;
+
+               for_each_tracing_cpu(cpu) {
+                       atomic_dec(&global_trace.data[cpu]->disabled);
+               }
+               tracing_on();
+       }
+
  out:
        spin_unlock_irqrestore(&ftrace_dump_lock, flags);
 }
 
+/* By default: disable tracing after the dump */
+void ftrace_dump(void)
+{
+       __ftrace_dump(true);
+}
+
 __init static int tracer_alloc_buffers(void)
 {
        struct trace_array_cpu *data;