[PATCH 4.14 19/22] tracing: Reverse the order of trace_types_lock and event_mutex
From: Greg Kroah-Hartman
Date: Fri May 08 2020 - 09:03:07 EST
From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
commit 12ecef0cb12102d8c034770173d2d1363cb97d52 upstream.
In order to make future changes where we need to call
tracing_set_clock() from within an event command, the order of
trace_types_lock and event_mutex must be reversed, as the event command
will hold event_mutex and the trace_types_lock is taken from within
tracing_set_clock().
Link: http://lkml.kernel.org/r/20170921162249.0dde3dca@xxxxxxxxxxxxxxxxxx
Requested-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Andress Kuo (éåä) <Andress.Kuo@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 5 +++++
kernel/trace/trace_events.c | 31 +++++++++++++++----------------
2 files changed, 20 insertions(+), 16 deletions(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7720,6 +7720,7 @@ static int instance_mkdir(const char *na
struct trace_array *tr;
int ret;
+ mutex_lock(&event_mutex);
mutex_lock(&trace_types_lock);
ret = -EEXIST;
@@ -7775,6 +7776,7 @@ static int instance_mkdir(const char *na
list_add(&tr->list, &ftrace_trace_arrays);
mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
return 0;
@@ -7786,6 +7788,7 @@ static int instance_mkdir(const char *na
out_unlock:
mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
return ret;
@@ -7798,6 +7801,7 @@ static int instance_rmdir(const char *na
int ret;
int i;
+ mutex_lock(&event_mutex);
mutex_lock(&trace_types_lock);
ret = -ENODEV;
@@ -7843,6 +7847,7 @@ static int instance_rmdir(const char *na
out_unlock:
mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
return ret;
}
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1403,8 +1403,8 @@ static int subsystem_open(struct inode *
return -ENODEV;
/* Make sure the system still exists */
- mutex_lock(&trace_types_lock);
mutex_lock(&event_mutex);
+ mutex_lock(&trace_types_lock);
list_for_each_entry(tr, &ftrace_trace_arrays, list) {
list_for_each_entry(dir, &tr->systems, list) {
if (dir == inode->i_private) {
@@ -1418,8 +1418,8 @@ static int subsystem_open(struct inode *
}
}
exit_loop:
- mutex_unlock(&event_mutex);
mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
if (!system)
return -ENODEV;
@@ -2305,15 +2305,15 @@ static void __add_event_to_tracers(struc
int trace_add_event_call(struct trace_event_call *call)
{
int ret;
- mutex_lock(&trace_types_lock);
mutex_lock(&event_mutex);
+ mutex_lock(&trace_types_lock);
ret = __register_event(call, NULL);
if (ret >= 0)
__add_event_to_tracers(call);
- mutex_unlock(&event_mutex);
mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
return ret;
}
@@ -2367,13 +2367,13 @@ int trace_remove_event_call(struct trace
{
int ret;
- mutex_lock(&trace_types_lock);
mutex_lock(&event_mutex);
+ mutex_lock(&trace_types_lock);
down_write(&trace_event_sem);
ret = probe_remove_event_call(call);
up_write(&trace_event_sem);
- mutex_unlock(&event_mutex);
mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
return ret;
}
@@ -2435,8 +2435,8 @@ static int trace_module_notify(struct no
{
struct module *mod = data;
- mutex_lock(&trace_types_lock);
mutex_lock(&event_mutex);
+ mutex_lock(&trace_types_lock);
switch (val) {
case MODULE_STATE_COMING:
trace_module_add_events(mod);
@@ -2445,8 +2445,8 @@ static int trace_module_notify(struct no
trace_module_remove_events(mod);
break;
}
- mutex_unlock(&event_mutex);
mutex_unlock(&trace_types_lock);
+ mutex_unlock(&event_mutex);
return 0;
}
@@ -2961,24 +2961,24 @@ create_event_toplevel_files(struct dentr
* creates the event hierachry in the @parent/events directory.
*
* Returns 0 on success.
+ *
+ * Must be called with event_mutex held.
*/
int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr)
{
int ret;
- mutex_lock(&event_mutex);
+ lockdep_assert_held(&event_mutex);
ret = create_event_toplevel_files(parent, tr);
if (ret)
- goto out_unlock;
+ goto out;
down_write(&trace_event_sem);
__trace_add_event_dirs(tr);
up_write(&trace_event_sem);
- out_unlock:
- mutex_unlock(&event_mutex);
-
+ out:
return ret;
}
@@ -3007,9 +3007,10 @@ early_event_add_tracer(struct dentry *pa
return ret;
}
+/* Must be called with event_mutex held */
int event_trace_del_tracer(struct trace_array *tr)
{
- mutex_lock(&event_mutex);
+ lockdep_assert_held(&event_mutex);
/* Disable any event triggers and associated soft-disabled events */
clear_event_triggers(tr);
@@ -3030,8 +3031,6 @@ int event_trace_del_tracer(struct trace_
tr->event_dir = NULL;
- mutex_unlock(&event_mutex);
-
return 0;
}