[PATCH 12/19] perf ftrace: add support for tracing children processes

[Changbin Du]

This adds an option '--trace-children' to allow us trace children
processes spawned by our target.

Signed-off-by: Changbin Du <changbin...@gmail.com>
---
 tools/perf/builtin-ftrace.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index ab76ba66bd9e..8fd95c109fe8 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -46,6 +46,7 @@ struct perf_ftrace {
        bool                    funcgraph_tail;
        bool                    long_info;
        unsigned                tracing_thresh;
+       bool                    trace_children;
 };
 
 struct filter_entry {
@@ -200,6 +201,7 @@ static void reset_tracing_options(struct perf_ftrace 
*ftrace __maybe_unused)
        write_tracing_option_file("irq-info", "0");
        write_tracing_option_file("userstacktrace", "0");
        write_tracing_option_file("sym-userobj", "0");
+       write_tracing_option_file("function-fork", "0");
 }
 
 static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
@@ -441,6 +443,17 @@ static int set_tracing_funcgraph_tail(struct perf_ftrace 
*ftrace)
        return 0;
 }
 
+static int set_tracing_trace_children(struct perf_ftrace *ftrace)
+{
+       if (!ftrace->trace_children)
+               return 0;
+
+       if (write_tracing_option_file("function-fork", "1") < 0)
+               return -1;
+
+       return 0;
+}
+
 static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char 
**argv)
 {
        char *trace_file;
@@ -539,6 +552,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int 
argc, const char **argv)
                goto out_reset;
        }
 
+       if (set_tracing_trace_children(ftrace) < 0) {
+               pr_err("failed to set tracing option function-fork\n");
+               goto out_reset;
+       }
+
        if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
                pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
                goto out_reset;
@@ -686,6 +704,8 @@ int cmd_ftrace(int argc, const char **argv)
                    "Show process names, PIDs, timestamps, irq-info if 
available"),
        OPT_UINTEGER(0, "tracing-thresh", &ftrace.tracing_thresh,
                     "Only show functions of which the duration is greater than 
<n>µs"),
+       OPT_BOOLEAN(0, "trace-children", &ftrace.trace_children,
+                   "Trace children processes"),
        OPT_END()
        };
 
-- 
2.25.1