On Fri, 17 Mar 2023 13:30:44 +0800 Cheng-Jui Wang cheng-jui.wang@mediatek.com wrote:
From: "Tze-nan Wu" Tze-nan.Wu@mediatek.com
Hi!
Thanks for the report and the patch. Some nits below.
Also change the subject to:
tracing/synthetic: Fix races on freeing last_cmd
kernel/trace/trace_events_synth.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index 46d0abb32d0f..ce438eccab2e 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -42,16 +42,25 @@ enum { ERRORS }; #undef C #define C(a, b) b +static DEFINE_MUTEX(lastcmd_mutex);
static const char *err_text[] = { ERRORS }; static char *last_cmd;
Please keep the mutex and the variable it protects next to each other:
static DEFINE_MUTEX(lastcmd_mutex); static char *last_cmd;
static int errpos(const char *str) {
- if (!str || !last_cmd)
return 0;
- int ret = 0;
- mutex_lock(&lastcmd_mutex);
- if (!str || !last_cmd) {
Change this to just:
if (!str || !last_cmd) goto out;
mutex_unlock(&lastcmd_mutex);return ret;
- }
- return err_pos(last_cmd, str);
- ret = err_pos(last_cmd, str);
Add:
out:
- mutex_unlock(&lastcmd_mutex);
- return ret;
} static void last_cmd_set(const char *str) @@ -59,18 +68,24 @@ static void last_cmd_set(const char *str) if (!str) return;
- mutex_lock(&lastcmd_mutex); kfree(last_cmd);
In this case, you can remove the space:
mutex_lock(&lastcmd_mutex); kfree(last_cmd); last_cmd = kstrdup(str, GFP_KERNEL); mutex_unlock(&lastcmd_mutex);
last_cmd = kstrdup(str, GFP_KERNEL);
- mutex_unlock(&lastcmd_mutex);
} static void synth_err(u8 err_type, u16 err_pos) {
- if (!last_cmd)
- mutex_lock(&lastcmd_mutex);
- if (!last_cmd) {
This should be:
if (!last_cmd) goto out;
mutex_unlock(&lastcmd_mutex);- }
tracing_log_err(NULL, "synthetic_events", last_cmd, err_text, err_type, err_pos);
out:
- mutex_unlock(&lastcmd_mutex);
} static int create_synth_event(const char *raw_command);
Thanks,
-- Steve