[ltt-dev] Updated TODO list before releasing LTTngbufferingtoLKML

[zhaolei@cn.fujitsu.com (Zhaolei)]

* Mathieu Desnoyers wrote:
>* Zhaolei (zhaolei at cn.fujitsu.com) wrote:
>> * Mathieu Desnoyers wrote:
>> >* Zhaolei (zhaolei at cn.fujitsu.com) 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);
>> >> 
>> >> 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++ )
>> >>         ...
>> >>     }
>> >> 
>> > 
>> > No, no...
>> > 
>> > only marker_update_probe_range() needs to be called form module.c, at
>> > load_module() and exit_module().
>> > 
>> > It will add a marker entry to the hash table when necessary, and
>> > increment/decrement the reference count of this marker entry. The marker
>> > entry can be removed from the hash table when the refcount falls to 0
>> > and no probe is registered on the marker.
>> > 
>> > At the same time the marker entry is added to the hash table, a
>> > debugfs mkdir is done. When the entry is removed from the hash table, a
>> > debugfs rmdir is done.
>> > 
>> > Is it a bit more clear ?
>> Hi, Mathieu
>> 
>> I see.
>> But IMHO, markers is used by lttng, but is not part of lttng.
>> So, i think source for create files in /debugfs/ltt/... should not be placed in
>> markers.c.
>> 
> 
> Let's put LTTng in /debugfs/trace/ then, along with markers. I think the
> LTTng name will eventually fade away as bits and pieces gets renamed as
> they are merged into mainline. :)
I understood.
OK, Let us try it.

> 
> Mathieu
> 
> 
>> > 
>> > Mathieu
>> > 
>> > 
>> > 
>> > 
>> >> _______________________________________________
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>> >> ltt-dev at lists.casi.polymtl.ca
>> >> http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
>> >> 
>> > 
>> > -- 
>> > Mathieu Desnoyers
>> > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
>> > 
>> >
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> 
> -- 
> Mathieu Desnoyers
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
> 
>