Re: [patch -mm] update mq_notify to use a struct pid

[Cedric Le Goater <clg@fr.ibm.com>]

Eric W. Biederman wrote:

> Cedric you mentioned a couple of other patches that are in flight.
> In the future could you please Cc: the containers list so independent
> efforts are less likely to duplicate work, and we are more likely
> to review each others patches instead?

yes sure, i was relying on the openvz wiki to avoid duplicated efforts on
this topic but i guess email is just the one and only tool for this kind of
development :)

[ ... ]

>>> Converting that is going to need some sysctl work, so I have been
>>> ignoring it temporarily.
>>>
>>> Filling in a struct pid through sysctl is extremely ugly at the
>>> moment, plus cad_pid needs some locking.
>> Which distros use /proc/sys/kernel/cad_pid and why ? I can image the need
>> but i didn't find much on the topic.
> 
> I'm not at all certain, and I'm not even certain I care.  The concept
> is there in the code so it needs to be dealt with.  

OK. It would be nice to make sure this is still in use before trying to
deal with /proc/sys/kernel/cad_pid.

> Although if I we extend the cad_pid concept it may make a difference.

what do you mean by extending cad_pid ? kill_init() ?

[ ... ]

>> is that about updating the siginfos in collect_signal() to hold the right
>> pid value depending on the pid namespace they are being received ?
> 
> Yes in send_signal, and in collect signal.  To make it work easily I needed
> to add a struct pid to struct sigqueue.  So in send_signal I generate
> the struct pid from the pid_t value and in collect signal I regenerate
> the numeric value.

OK. That's what i imagined also but we need a bit more of the pid namespace
to regenerate the numerical value. So, how will you convert this 'struct
pid*' in a pid value using the current pid namespace ?

thinking aloud :

* if the pid namespace of the sending struct pid and current match,
	use nr.
* if they don't,
	if the sending pid namespace is the ancestor of the current pid
	namespace
		use 0
	else
		it's a bug.

struct pid* needs a pid namespace attribute and pid namespace needs to know
its parent.

C.