From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
stable@vger.kernel.org, Tom Zanussi <zanussi@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: [for-linus][PATCH 3/5] tracing: trigger: Replace unneeded RCU-list traversals
Date: Tue, 21 Jan 2020 09:38:50 -0500 [thread overview]
Message-ID: <20200121143956.757178876@goodmis.org> (raw)
In-Reply-To: 20200121143847.609307852@goodmis.org
From: Masami Hiramatsu <mhiramat@kernel.org>
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.
Link: http://lkml.kernel.org/r/157680910305.11685.15110237954275915782.stgit@devnote2
Cc: stable@vger.kernel.org
Fixes: 30350d65ac567 ("tracing: Add variable support to hist triggers")
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.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 f62de5f43e79..d33b046f985a 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1766,11 +1766,13 @@ 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);
@@ -1820,7 +1822,9 @@ 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);
@@ -3115,7 +3119,9 @@ 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;
@@ -3166,9 +3172,11 @@ 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;
@@ -5528,7 +5536,7 @@ 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++);
}
@@ -5921,7 +5929,9 @@ 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;
@@ -6005,10 +6015,12 @@ 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;
@@ -6026,10 +6038,12 @@ 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;
@@ -6051,10 +6065,12 @@ 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;
@@ -6080,7 +6096,9 @@ 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))
@@ -6323,7 +6341,8 @@ 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 ==
--
2.24.1
next prev parent reply other threads:[~2020-01-21 14:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-21 14:38 [for-linus][PATCH 0/5] tracing: Fixes for 5.5 Steven Rostedt
2020-01-21 14:38 ` [for-linus][PATCH 1/5] tracing: xen: Ordered comparison of function pointers Steven Rostedt
2020-01-21 14:38 ` [for-linus][PATCH 2/5] tracing/uprobe: Fix double perf_event linking on multiprobe uprobe Steven Rostedt
2020-01-21 14:50 ` Peter Zijlstra
2020-01-21 14:59 ` David Laight
2020-01-21 15:06 ` Peter Zijlstra
2020-01-22 22:12 ` Masami Hiramatsu
2020-01-21 14:38 ` Steven Rostedt [this message]
[not found] ` <20200122022623.20D812465A@mail.kernel.org>
2020-01-22 3:32 ` [for-linus][PATCH 3/5] tracing: trigger: Replace unneeded RCU-list traversals Masami Hiramatsu
2020-01-21 14:38 ` [for-linus][PATCH 4/5] tracing: Fix histogram code when expression has same var as value Steven Rostedt
2020-01-21 14:38 ` [for-linus][PATCH 5/5] tracing: Do not set trace clock if tracefs lockdown is in effect Steven Rostedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200121143956.757178876@goodmis.org \
--to=rostedt@goodmis.org \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@kernel.org \
--cc=mingo@kernel.org \
--cc=stable@vger.kernel.org \
--cc=zanussi@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox