Messages in this thread |  | | Date | Tue, 7 Jan 2020 18:15:00 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH -tip] tracing: trigger: Replace unneeded RCU-list traversals |
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Hi Tom,
Could you review this fix?
On Fri, 20 Dec 2019 11:31:43 +0900 Masami Hiramatsu <mhiramat@kernel.org> wrote:
> With CONFIG_PROVE_RCU_LIST, I had many suspicious RCU warnings > when I ran ftracetest trigger testcases. > > ----- > # dmesg -c > /dev/null > # ./ftracetest test.d/trigger > ... > # dmesg | grep "RCU-list traversed" | cut -f 2 -d ] | cut -f 2 -d " " > kernel/trace/trace_events_hist.c:6070 > kernel/trace/trace_events_hist.c:1760 > kernel/trace/trace_events_hist.c:5911 > kernel/trace/trace_events_trigger.c:504 > kernel/trace/trace_events_hist.c:1810 > kernel/trace/trace_events_hist.c:3158 > kernel/trace/trace_events_hist.c:3105 > kernel/trace/trace_events_hist.c:5518 > kernel/trace/trace_events_hist.c:5998 > kernel/trace/trace_events_hist.c:6019 > kernel/trace/trace_events_hist.c:6044 > kernel/trace/trace_events_trigger.c:1500 > kernel/trace/trace_events_trigger.c:1540 > kernel/trace/trace_events_trigger.c:539 > kernel/trace/trace_events_trigger.c:584 > ----- > > I investigated those warnings and found that the RCU-list > traversals in event trigger and hist didn't need to use > RCU version because those were called only under event_mutex. > > I also checked other RCU-list traversals related to event > trigger list, and found that most of them were called from > event_hist_trigger_func() or hist_unregister_trigger() or > register/unregister functions except for a few cases. > > Replace these unneeded RCU-list traversals with normal list > traversal macro and lockdep_assert_held() to check the > event_mutex is held. > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > --- > kernel/trace/trace_events_hist.c | 41 ++++++++++++++++++++++++++--------- > kernel/trace/trace_events_trigger.c | 20 +++++++++++++---- > 2 files changed, 45 insertions(+), 16 deletions(-) > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > index 23b0195ac977..844f8325077f 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -1753,11 +1753,13 @@ static struct hist_field *find_var(struct hist_trigger_data *hist_data, > struct event_trigger_data *test; > struct hist_field *hist_field; > > + lockdep_assert_held(&event_mutex); > + > hist_field = find_var_field(hist_data, var_name); > if (hist_field) > return hist_field; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > test_data = test->private_data; > hist_field = find_var_field(test_data, var_name); > @@ -1807,7 +1809,9 @@ static struct hist_field *find_file_var(struct trace_event_file *file, > struct event_trigger_data *test; > struct hist_field *hist_field; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > test_data = test->private_data; > hist_field = find_var_field(test_data, var_name); > @@ -3102,7 +3106,9 @@ static char *find_trigger_filter(struct hist_trigger_data *hist_data, > { > struct event_trigger_data *test; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > if (test->private_data == hist_data) > return test->filter_str; > @@ -3153,9 +3159,11 @@ find_compatible_hist(struct hist_trigger_data *target_hist_data, > struct event_trigger_data *test; > unsigned int n_keys; > > + lockdep_assert_held(&event_mutex); > + > n_keys = target_hist_data->n_fields - target_hist_data->n_vals; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > hist_data = test->private_data; > > @@ -5515,7 +5523,7 @@ static int hist_show(struct seq_file *m, void *v) > goto out_unlock; > } > > - list_for_each_entry_rcu(data, &event_file->triggers, list) { > + list_for_each_entry(data, &event_file->triggers, list) { > if (data->cmd_ops->trigger_type == ETT_EVENT_HIST) > hist_trigger_show(m, data, n++); > } > @@ -5908,7 +5916,9 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops, > if (hist_data->attrs->name && !named_data) > goto new; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > if (!hist_trigger_match(data, test, named_data, false)) > continue; > @@ -5992,10 +6002,12 @@ static bool have_hist_trigger_match(struct event_trigger_data *data, > struct event_trigger_data *test, *named_data = NULL; > bool match = false; > > + lockdep_assert_held(&event_mutex); > + > if (hist_data->attrs->name) > named_data = find_named_trigger(hist_data->attrs->name); > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > if (hist_trigger_match(data, test, named_data, false)) { > match = true; > @@ -6013,10 +6025,12 @@ static bool hist_trigger_check_refs(struct event_trigger_data *data, > struct hist_trigger_data *hist_data = data->private_data; > struct event_trigger_data *test, *named_data = NULL; > > + lockdep_assert_held(&event_mutex); > + > if (hist_data->attrs->name) > named_data = find_named_trigger(hist_data->attrs->name); > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > if (!hist_trigger_match(data, test, named_data, false)) > continue; > @@ -6038,10 +6052,12 @@ static void hist_unregister_trigger(char *glob, struct event_trigger_ops *ops, > struct event_trigger_data *test, *named_data = NULL; > bool unregistered = false; > > + lockdep_assert_held(&event_mutex); > + > if (hist_data->attrs->name) > named_data = find_named_trigger(hist_data->attrs->name); > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > if (!hist_trigger_match(data, test, named_data, false)) > continue; > @@ -6067,7 +6083,9 @@ static bool hist_file_check_refs(struct trace_event_file *file) > struct hist_trigger_data *hist_data; > struct event_trigger_data *test; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > hist_data = test->private_data; > if (check_var_refs(hist_data)) > @@ -6310,7 +6328,8 @@ hist_enable_trigger(struct event_trigger_data *data, void *rec, > struct enable_trigger_data *enable_data = data->private_data; > struct event_trigger_data *test; > > - list_for_each_entry_rcu(test, &enable_data->file->triggers, list) { > + list_for_each_entry_rcu(test, &enable_data->file->triggers, list, > + lockdep_is_held(&event_mutex)) { > if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) { > if (enable_data->enable) > test->paused = false; > diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c > index 2cd53ca21b51..40106fff06a4 100644 > --- a/kernel/trace/trace_events_trigger.c > +++ b/kernel/trace/trace_events_trigger.c > @@ -501,7 +501,9 @@ void update_cond_flag(struct trace_event_file *file) > struct event_trigger_data *data; > bool set_cond = false; > > - list_for_each_entry_rcu(data, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(data, &file->triggers, list) { > if (data->filter || event_command_post_trigger(data->cmd_ops) || > event_command_needs_rec(data->cmd_ops)) { > set_cond = true; > @@ -536,7 +538,9 @@ static int register_trigger(char *glob, struct event_trigger_ops *ops, > struct event_trigger_data *test; > int ret = 0; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(test, &file->triggers, list) { > if (test->cmd_ops->trigger_type == data->cmd_ops->trigger_type) { > ret = -EEXIST; > goto out; > @@ -581,7 +585,9 @@ static void unregister_trigger(char *glob, struct event_trigger_ops *ops, > struct event_trigger_data *data; > bool unregistered = false; > > - list_for_each_entry_rcu(data, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(data, &file->triggers, list) { > if (data->cmd_ops->trigger_type == test->cmd_ops->trigger_type) { > unregistered = true; > list_del_rcu(&data->list); > @@ -1497,7 +1503,9 @@ int event_enable_register_trigger(char *glob, > struct event_trigger_data *test; > int ret = 0; > > - list_for_each_entry_rcu(test, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(test, &file->triggers, list) { > test_enable_data = test->private_data; > if (test_enable_data && > (test->cmd_ops->trigger_type == > @@ -1537,7 +1545,9 @@ void event_enable_unregister_trigger(char *glob, > struct event_trigger_data *data; > bool unregistered = false; > > - list_for_each_entry_rcu(data, &file->triggers, list) { > + lockdep_assert_held(&event_mutex); > + > + list_for_each_entry(data, &file->triggers, list) { > enable_data = data->private_data; > if (enable_data && > (data->cmd_ops->trigger_type == >
-- Masami Hiramatsu <mhiramat@kernel.org>
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