When executing the command "perf list", I met "Error: failed to open
tracing events directory" twice, the first reason is that there is no
"/sys/kernel/tracing/events" directory due to it does not enable the
kernel tracing infrastructure with CONFIG_FTRACE, the second reason
is that there is no root privileges.
Add the error string to tell the users what happened and what should
to do, and also call put_tracing_file() to free events_path a little
later to avoid messy code in the error message.
At the same time, just remove the redundant "/" of the file path in
the function get_tracing_file(), otherwise it shows something like
"/sys/kernel/tracing//events".
Before:
$ ./perf list
Error: failed to open tracing events directory
After:
(1) Without CONFIG_FTRACE
$ ./perf list
Error: failed to open tracing events directory
/sys/kernel/tracing/events: No such file or directory
(2) With CONFIG_FTRACE but no root privileges
$ ./perf list
Error: failed to open tracing events directory
/sys/kernel/tracing/events: Permission denied
Committer testing:
Redirect stdout to null to quickly test the patch:
Before:
$ perf list > /dev/null
Error: failed to open tracing events directory
$
After:
$ perf list > /dev/null
Error: failed to open tracing events directory
/sys/kernel/tracing/events: Permission denied
$
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/20240730062301.23244-3-yangtiezhu@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
{
char *file;
- if (asprintf(&file, "%s/%s", tracing_path_mount(), name) < 0)
+ if (asprintf(&file, "%s%s", tracing_path_mount(), name) < 0)
return NULL;
return file;
struct dirent **sys_namelist = NULL;
int sys_items;
- put_tracing_file(events_path);
if (events_fd < 0) {
pr_err("Error: failed to open tracing events directory\n");
+ pr_err("%s: %s\n", events_path, strerror(errno));
return;
}
+ put_tracing_file(events_path);
sys_items = tracing_events__scandir_alphasort(&sys_namelist);