Merge branch 'linus' into tracing/hw-branch-tracing

Merge reason: update to latest tracing and ptrace APIs

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 69 insertions, 11 deletions

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index b91091267067..499d01c44cd1 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -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;