1 files changed, 65 insertions, 3 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 4edb4b74eb7e..39ada66389cc 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -47,6 +47,8 @@ struct fgraph_data {
 #define TRACE_GRAPH_PRINT_ABS_TIME      0x20
 #define TRACE_GRAPH_PRINT_IRQS          0x40
 
+static unsigned int max_depth;
+
 static struct tracer_opt trace_opts[] = {
         /* Display overruns? (for self-debug purpose) */
         { TRACER_OPT(funcgraph-overrun, TRACE_GRAPH_PRINT_OVERRUN) },
@@ -189,10 +191,16 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 
         ftrace_pop_return_trace(&trace, &ret, frame_pointer);
         trace.rettime = trace_clock_local();
-        ftrace_graph_return(&trace);
         barrier();
         current->curr_ret_stack--;
 
+        /*
+         * The trace should run after decrementing the ret counter
+         * in case an interrupt were to come in. We don't want to
+         * lose the interrupt if max_depth is set.
+         */
+        ftrace_graph_return(&trace);
+
         if (unlikely(!ret)) {
                 ftrace_graph_stop();
                 WARN_ON(1);
@@ -250,8 +258,9 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
                 return 0;
 
         /* trace it when it is-nested-in or is a function enabled. */
-        if (!(trace->depth || ftrace_graph_addr(trace->func)) ||
-              ftrace_graph_ignore_irqs())
+        if ((!(trace->depth || ftrace_graph_addr(trace->func)) ||
+             ftrace_graph_ignore_irqs()) ||
+            (max_depth && trace->depth >= max_depth))
                 return 0;
 
         local_irq_save(flags);
@@ -1457,6 +1466,59 @@ static struct tracer graph_trace __read_mostly = {
 #endif
 };
 
+
+static ssize_t
+graph_depth_write(struct file *filp, const char __user *ubuf, size_t cnt,
+                  loff_t *ppos)
+{
+        unsigned long val;
+        int ret;
+
+        ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
+        if (ret)
+                return ret;
+
+        max_depth = val;
+
+        *ppos += cnt;
+
+        return cnt;
+}
+
+static ssize_t
+graph_depth_read(struct file *filp, char __user *ubuf, size_t cnt,
+                 loff_t *ppos)
+{
+        char buf[15]; /* More than enough to hold UINT_MAX + "\n"*/
+        int n;
+
+        n = sprintf(buf, "%d\n", max_depth);
+
+        return simple_read_from_buffer(ubuf, cnt, ppos, buf, n);
+}
+
+static const struct file_operations graph_depth_fops = {
+        .open           = tracing_open_generic,
+        .write          = graph_depth_write,
+        .read           = graph_depth_read,
+        .llseek         = generic_file_llseek,
+};
+
+static __init int init_graph_debugfs(void)
+{
+        struct dentry *d_tracer;
+
+        d_tracer = tracing_init_dentry();
+        if (!d_tracer)
+                return 0;
+
+        trace_create_file("max_graph_depth", 0644, d_tracer,
+                          NULL, &graph_depth_fops);
+
+        return 0;
+}
+fs_initcall(init_graph_debugfs);
+
 static __init int init_graph_trace(void)
 {
         max_bytes_for_cpu = snprintf(NULL, 0, "%d", nr_cpu_ids - 1);