[ltt-dev] Updated TODO list before releasing LTTng bufferingtoLKML

[Zhaolei]

* Zhaolei wrote:
>* Mathieu Desnoyers wrote:
>>> > - move ltt/ltt-marker-control.c /proc interface to debugfs
>>> >  I think we should integrate its directory tree to the new LTTng tracer
>>> >  debugfs API like this :
>>> > 
>>> >  /debugfs/ltt/events/buffer_name/marker_name/
>>> >    where we find files like :
>>> >    state
>>> >      write : 1/0 (on/off)
>>> >      read  : 1/0 (on/off)
>>> >    format
>>> >      read : marker format string
>>> Hello, Mathieu,
>>> 
>>> So we need to create a marker's debugfs-directory when user insmod
>>>  a module with markers.
>>> But i think we don't have a callback when user insmod, and we
>>>  should avoid to patch kernel/module.c for this kind of function.
>>> 
>>> So, maybe we can only "echo marker_name 0/1" > marker-control.
>>> Dou you have suggestion for me?
>>> 
>> 
>> 
>> Yes, we do have a callback in insmod.
>> 
>> See :
>> 
>> load_module()
>> 
>> #ifdef CONFIG_MARKERS
>>        if (!mod->taints)
>>                marker_update_probe_range(mod->markers,
>>                        mod->markers + mod->num_markers);
>> #endif
>> 
>> We would probably also have to get a callback in free_module to remove
>> the marker directory entry when the last marker reference is gone. The
>> same
>> 
>> #ifdef CONFIG_MARKERS
>>        if (!mod->taints)
>>                marker_update_probe_range(mod->markers,
>>                        mod->markers + mod->num_markers);
>> #endif
>> 
>> Could probably be used in free_module.
>> 
> Do you means we insert another callback as markers do?
> as example in insmod:
> #ifdef CONFIG_MARKERS
>    if (!mod->taints)
>        marker_update_probe_range(mod->markers,
>         mod->markers + mod->num_markers);
> #endif
> #ifdef CONFIG_LTT
>    if (!mod->taints)
>        lttctl_create_dirs(mod->markers,
>        mod->markers + mod->num_markers);
> #endif
> 
> It it is true, i think because ltt_control will be a kernel module, and we can't
> call a module's function in load_module().
> 
> So, maybe we can do as following:
> 1: make module.c support callbackset.
>  add following functions to module.c
>  module_register_callback(enum MODULE_CALLBACK_TYPE type, callback_func func);
>  module_unregister_callback(LOAD_MODULE, callback_func func);
Sorry for my mistake
module_unregister_callback(LOAD_MODULE, callback_func func);
-> module_unregister_callback(enum MODULE_CALLBACK_TYPE type, callback_func func);

> 
> 2: make marks and ltt_control use new function
>  example if ltt_control's
>  init() {module_register_callback(LOAD_MODULE, create_debugfs_dir);}
>  exit() {module_unregister_callback(LOAD_MODULE, free_debugfs_dir);}
>  void create_debugfs_dir(struct module *mod) {
>    for (i = 0; i < mod->num_markers; i++ )
>        ...
>    }
> 
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