Merge branch 'linus' into tracing/hw-branch-tracing
[sfrench/cifs-2.6.git] / kernel / trace / trace_selftest.c
index b91091267067651c7e54d8136726b2b27c1dd675..499d01c44cd17b9a95e843b5b062b900185c4886 100644 (file)
@@ -250,6 +250,28 @@ trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
 
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+/* Maximum number of functions to trace before diagnosing a hang */
+#define GRAPH_MAX_FUNC_TEST    100000000
+
+static void __ftrace_dump(bool disable_tracing);
+static unsigned int graph_hang_thresh;
+
+/* Wrap the real function entry probe to avoid possible hanging */
+static int trace_graph_entry_watchdog(struct ftrace_graph_ent *trace)
+{
+       /* This is harmlessly racy, we want to approximately detect a hang */
+       if (unlikely(++graph_hang_thresh > GRAPH_MAX_FUNC_TEST)) {
+               ftrace_graph_stop();
+               printk(KERN_WARNING "BUG: Function graph tracer hang!\n");
+               if (ftrace_dump_on_oops)
+                       __ftrace_dump(false);
+               return 0;
+       }
+
+       return trace_graph_entry(trace);
+}
+
 /*
  * Pretty much the same than for the function tracer from which the selftest
  * has been borrowed.
@@ -261,15 +283,29 @@ trace_selftest_startup_function_graph(struct tracer *trace,
        int ret;
        unsigned long count;
 
-       ret = tracer_init(trace, tr);
+       /*
+        * Simulate the init() callback but we attach a watchdog callback
+        * to detect and recover from possible hangs
+        */
+       tracing_reset_online_cpus(tr);
+       ret = register_ftrace_graph(&trace_graph_return,
+                                   &trace_graph_entry_watchdog);
        if (ret) {
                warn_failed_init_tracer(trace, ret);
                goto out;
        }
+       tracing_start_cmdline_record();
 
        /* Sleep for a 1/10 of a second */
        msleep(100);
 
+       /* Have we just recovered from a hang? */
+       if (graph_hang_thresh > GRAPH_MAX_FUNC_TEST) {
+               tracing_selftest_disabled = true;
+               ret = -1;
+               goto out;
+       }
+
        tracing_stop();
 
        /* check the trace buffer */
@@ -317,6 +353,14 @@ trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)
        local_irq_disable();
        udelay(100);
        local_irq_enable();
+
+       /*
+        * Stop the tracer to avoid a warning subsequent
+        * to buffer flipping failure because tracing_stop()
+        * disables the tr and max buffers, making flipping impossible
+        * in case of parallels max irqs off latencies.
+        */
+       trace->stop(tr);
        /* stop the tracing. */
        tracing_stop();
        /* check both trace buffers */
@@ -371,6 +415,14 @@ trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr)
        preempt_disable();
        udelay(100);
        preempt_enable();
+
+       /*
+        * Stop the tracer to avoid a warning subsequent
+        * to buffer flipping failure because tracing_stop()
+        * disables the tr and max buffers, making flipping impossible
+        * in case of parallels max preempt off latencies.
+        */
+       trace->stop(tr);
        /* stop the tracing. */
        tracing_stop();
        /* check both trace buffers */
@@ -416,7 +468,7 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
        ret = tracer_init(trace, tr);
        if (ret) {
                warn_failed_init_tracer(trace, ret);
-               goto out;
+               goto out_no_start;
        }
 
        /* reset the max latency */
@@ -430,31 +482,35 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
        /* reverse the order of preempt vs irqs */
        local_irq_enable();
 
+       /*
+        * Stop the tracer to avoid a warning subsequent
+        * to buffer flipping failure because tracing_stop()
+        * disables the tr and max buffers, making flipping impossible
+        * in case of parallels max irqs/preempt off latencies.
+        */
+       trace->stop(tr);
        /* stop the tracing. */
        tracing_stop();
        /* check both trace buffers */
        ret = trace_test_buffer(tr, NULL);
-       if (ret) {
-               tracing_start();
+       if (ret)
                goto out;
-       }
 
        ret = trace_test_buffer(&max_tr, &count);
-       if (ret) {
-               tracing_start();
+       if (ret)
                goto out;
-       }
 
        if (!ret && !count) {
                printk(KERN_CONT ".. no entries found ..");
                ret = -1;
-               tracing_start();
                goto out;
        }
 
        /* do the test by disabling interrupts first this time */
        tracing_max_latency = 0;
        tracing_start();
+       trace->start(tr);
+
        preempt_disable();
        local_irq_disable();
        udelay(100);
@@ -462,6 +518,7 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
        /* reverse the order of preempt vs irqs */
        local_irq_enable();
 
+       trace->stop(tr);
        /* stop the tracing. */
        tracing_stop();
        /* check both trace buffers */
@@ -477,9 +534,10 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
                goto out;
        }
 
- out:
-       trace->reset(tr);
+out:
        tracing_start();
+out_no_start:
+       trace->reset(tr);
        tracing_max_latency = save_max;
 
        return ret;