diff mbox series

[3/3] trace: Try using tracefs first

Message ID 20171107153136.19426-3-namhyung@gmail.com
State New
Headers show
Series [1/3] trace: Simplify find_debugfs() | expand

Commit Message

Namhyung Kim Nov. 7, 2017, 3:31 p.m. UTC 
Recent Linux kernel provides separate tracefs which doesn't need to be
mounted on the debugfs.  Although most systems mount it at the
traditional place on the debugfs, it'd be safer to check tracefs first.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
---
 trace/ftrace.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/trace/ftrace.c b/trace/ftrace.c
index 213cb2205f..61692a8682 100644
--- a/trace/ftrace.c
+++ b/trace/ftrace.c
@@ -42,12 +42,18 @@  bool ftrace_init(void)
 {
     char mount_point[PATH_MAX];
     char path[PATH_MAX];
-    int debugfs_found;
+    int tracefs_found;
     int trace_fd = -1;
+    const char *subdir = "";
 
-    debugfs_found = find_mount(mount_point, "debugfs");
-    if (debugfs_found) {
-        snprintf(path, PATH_MAX, "%s/tracing/tracing_on", mount_point);
+    tracefs_found = find_mount(mount_point, "tracefs");
+    if (!tracefs_found) {
+        tracefs_found = find_mount(mount_point, "debugfs");
+        subdir = "/tracing";
+    }
+
+    if (tracefs_found) {
+        snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir);
         trace_fd = open(path, O_WRONLY);
         if (trace_fd < 0) {
             if (errno == EACCES) {
@@ -66,14 +72,14 @@  bool ftrace_init(void)
             }
             close(trace_fd);
         }
-        snprintf(path, PATH_MAX, "%s/tracing/trace_marker", mount_point);
+        snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir);
         trace_marker_fd = open(path, O_WRONLY);
         if (trace_marker_fd < 0) {
             perror("Could not open ftrace 'trace_marker' file");
             return false;
         }
     } else {
-        fprintf(stderr, "debugfs is not mounted\n");
+        fprintf(stderr, "tracefs is not mounted\n");
         return false;
     }