trace: Move trace event enable from fs_initcall to core_initcall

This patch splits trace event initialization in two stages:
 * ftrace enable
 * sysfs event entry creation

This allows to capture trace events from an earlier point
by using 'trace_event' kernel parameter and is important
to trace boot-up allocations.

Note that, in order to enable events at core_initcall,
it's necessary to move init_ftrace_syscalls() from
core_initcall to early_initcall.

Link: http://lkml.kernel.org/r/1347461277-25302-1-git-send-email-elezegarcia@gmail.com

Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 73 insertions, 37 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index bbb0e63d78e..d608d09d08c 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1199,6 +1199,31 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
         return 0;
 }
 
+static void event_remove(struct ftrace_event_call *call)
+{
+        ftrace_event_enable_disable(call, 0);
+        if (call->event.funcs)
+                __unregister_ftrace_event(&call->event);
+        list_del(&call->list);
+}
+
+static int event_init(struct ftrace_event_call *call)
+{
+        int ret = 0;
+
+        if (WARN_ON(!call->name))
+                return -EINVAL;
+
+        if (call->class->raw_init) {
+                ret = call->class->raw_init(call);
+                if (ret < 0 && ret != -ENOSYS)
+                        pr_warn("Could not initialize trace events/%s\n",
+                                call->name);
+        }
+
+        return ret;
+}
+
 static int
 __trace_add_event_call(struct ftrace_event_call *call, struct module *mod,
                        const struct file_operations *id,
@@ -1209,19 +1234,9 @@ __trace_add_event_call(struct ftrace_event_call *call, struct module *mod,
         struct dentry *d_events;
         int ret;
 
-        /* The linker may leave blanks */
-        if (!call->name)
-                return -EINVAL;
-
-        if (call->class->raw_init) {
-                ret = call->class->raw_init(call);
-                if (ret < 0) {
-                        if (ret != -ENOSYS)
-                                pr_warning("Could not initialize trace events/%s\n",
-                                           call->name);
-                        return ret;
-                }
-        }
+        ret = event_init(call);
+        if (ret < 0)
+                return ret;
 
         d_events = event_trace_events_dir();
         if (!d_events)
@@ -1272,13 +1287,10 @@ static void remove_subsystem_dir(const char *name)
  */
 static void __trace_remove_event_call(struct ftrace_event_call *call)
 {
-        ftrace_event_enable_disable(call, 0);
-        if (call->event.funcs)
-                __unregister_ftrace_event(&call->event);
-        debugfs_remove_recursive(call->dir);
-        list_del(&call->list);
+        event_remove(call);
         trace_destroy_fields(call);
         destroy_preds(call);
+        debugfs_remove_recursive(call->dir);
         remove_subsystem_dir(call->class->system);
 }
 
@@ -1450,15 +1462,43 @@ static __init int setup_trace_event(char *str)
 }
 __setup("trace_event=", setup_trace_event);
 
+static __init int event_trace_enable(void)
+{
+        struct ftrace_event_call **iter, *call;
+        char *buf = bootup_event_buf;
+        char *token;
+        int ret;
+
+        for_each_event(iter, __start_ftrace_events, __stop_ftrace_events) {
+
+                call = *iter;
+                ret = event_init(call);
+                if (!ret)
+                        list_add(&call->list, &ftrace_events);
+        }
+
+        while (true) {
+                token = strsep(&buf, ",");
+
+                if (!token)
+                        break;
+                if (!*token)
+                        continue;
+
+                ret = ftrace_set_clr_event(token, 1);
+                if (ret)
+                        pr_warn("Failed to enable trace event: %s\n", token);
+        }
+        return 0;
+}
+
 static __init int event_trace_init(void)
 {
-        struct ftrace_event_call **call;
+        struct ftrace_event_call *call;
         struct dentry *d_tracer;
         struct dentry *entry;
         struct dentry *d_events;
         int ret;
-        char *buf = bootup_event_buf;
-        char *token;
 
         d_tracer = tracing_init_dentry();
         if (!d_tracer)
@@ -1497,24 +1537,19 @@ static __init int event_trace_init(void)
         if (trace_define_common_fields())
                 pr_warning("tracing: Failed to allocate common fields");
 
-        for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
-                __trace_add_event_call(*call, NULL, &ftrace_event_id_fops,
+        /*
+         * Early initialization already enabled ftrace event.
+         * Now it's only necessary to create the event directory.
+         */
+        list_for_each_entry(call, &ftrace_events, list) {
+
+                ret = event_create_dir(call, d_events,
+                                       &ftrace_event_id_fops,
                                        &ftrace_enable_fops,
                                        &ftrace_event_filter_fops,
                                        &ftrace_event_format_fops);
-        }
-
-        while (true) {
-                token = strsep(&buf, ",");
-
-                if (!token)
-                        break;
-                if (!*token)
-                        continue;
-
-                ret = ftrace_set_clr_event(token, 1);
-                if (ret)
-                        pr_warning("Failed to enable trace event: %s\n", token);
+                if (ret < 0)
+                        event_remove(call);
         }
 
         ret = register_module_notifier(&trace_module_nb);
@@ -1523,6 +1558,7 @@ static __init int event_trace_init(void)
 
         return 0;
 }
+core_initcall(event_trace_enable);
 fs_initcall(event_trace_init);
 
 #ifdef CONFIG_FTRACE_STARTUP_TEST
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 6b245f64c8d..2485a7d09b1 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -487,7 +487,7 @@ int __init init_ftrace_syscalls(void)
 
         return 0;
 }
-core_initcall(init_ftrace_syscalls);
+early_initcall(init_ftrace_syscalls);
 
 #ifdef CONFIG_PERF_EVENTS