> On Sep 9, 2022, at 4:58 AM, Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxx> wrote:
>
> Song Liu wrote:
[...]
>> +
>> /**
>> * register_ftrace_function - register a function for profiling
>> * @ops: ops structure that holds the function for profiling.
>> @@ -8018,14 +8206,15 @@ int register_ftrace_function(struct ftrace_ops *ops)
>> {
>> int ret;
>> - ftrace_ops_init(ops);
>> -
>> - mutex_lock(&ftrace_lock);
>> -
>> - ret = ftrace_startup(ops, 0);
>> + lock_direct_mutex();
>
> Trying to enable ftrace direct on powerpc, this is resulting in a hung task when testing samples/ftrace/ftrace-direct-modify.c
>
> Essentially, the sample calls modify_ftrace_direct(), which grabs direct_mutex before calling ftrace_modify_direct_caller()->register_ftrace_function().
>
Thanks for the report. Would the following change fix the issue?
Song
diff --git i/kernel/trace/ftrace.c w/kernel/trace/ftrace.c
index bc921a3f7ea8..2f1e6cfa834e 100644
--- i/kernel/trace/ftrace.c
+++ w/kernel/trace/ftrace.c
@@ -5496,7 +5496,7 @@ int __weak ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
if (ret)
goto out_lock;
- ret = register_ftrace_function(&stub_ops);
+ ret = register_ftrace_function_nolock(&stub_ops);
if (ret) {
ftrace_set_filter_ip(&stub_ops, ip, 1, 0);
goto out_lock;
>
> - Naveen
>
>
>> + ret = prepare_direct_functions_for_ipmodify(ops);
>> + if (ret < 0)
>> + goto out_unlock;
>> - mutex_unlock(&ftrace_lock);
>> + ret = register_ftrace_function_nolock(ops);
>> +out_unlock:
>> + unlock_direct_mutex();
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(register_ftrace_function);
>> @@ -8044,6 +8233,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
>> ret = ftrace_shutdown(ops, 0);
>> mutex_unlock(&ftrace_lock);
>> + cleanup_direct_functions_after_ipmodify(ops);
>> return ret;
>> }
>> EXPORT_SYMBOL_GPL(unregister_ftrace_function);
>> --
>> 2.30.2
