When linux is built without support for function graph tracer, the ftrace
builtin of perf will fail when trying to reset max_graph_depth because the
file does not exist. This prevents the use of function tracer from perf.
Only try to write the file max_graph_depth file when it exists.
Signed-off-by: Julien Thierry <julien.thie...@arm.com>
Cc: Will Deacon <will.dea...@arm.com>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: linux-kernel@vger.kernel.org
---
tools/perf/builtin-ftrace.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 25a42ac..1abc066 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -14,6 +14,7 @@
#include <signal.h>
#include <fcntl.h>
#include <poll.h>
+#include <sys/stat.h>
#include "debug.h"
#include <subcmd/parse-options.h>
@@ -116,6 +117,13 @@ static int append_tracing_file(const char *name, const
char *val)
static int reset_tracing_cpu(void);
static void reset_tracing_filters(void);
+static inline bool tracing_file_accessible(const char *name)
+{
+ struct stat s;
+
+ return stat(get_tracing_file(name), &s) == 0;
+}
+
static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
{
if (write_tracing_file("tracing_on", "0") < 0)
@@ -130,8 +138,12 @@ static int reset_tracing_files(struct perf_ftrace *ftrace
__maybe_unused)
if (reset_tracing_cpu() < 0)
return -1;
- if (write_tracing_file("max_graph_depth", "0") < 0)
+ if (!tracing_file_accessible("max_graph_depth")) {
+ if (!strcmp(ftrace->tracer, "function_graph"))
+ return -1;
+ } else if (write_tracing_file("max_graph_depth", "0") < 0) {
return -1;
+ }
reset_tracing_filters();
return 0;
--
1.9.1
