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

[compudj@krystal.dyndns.org (Mathieu Desnoyers)]

* 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. :)

Mathieu


> > 
> > Mathieu
> > 
> > 
> > 
> > 
> >> _______________________________________________
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> >> ltt-dev at lists.casi.polymtl.ca
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> >> 
> > 
> > -- 
> > 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