Re: [Patch][RFC] Disabling per-tgid stats on task exit in taskstats

Shailabh,

On Tue, 2006-04-07 at 12:37 -0400, Shailabh Nagar wrote:
[..]

Here's a strawman for the problem we're trying to solve: get
notification of the close of a NETLINK_GENERIC socket that had
been used to register interest for some cpus within taskstats.

 From looking at the netlink code, the way to go seems to be

- it maintains a pidhash of nl_pids that are currently
registered to listen to atleast one cpu. It also stores the
cpumask used.
- taskstats registers a notifier block within netlink_chain
and receives a callback on the NETLINK_URELEASE event, similar
to drivers/scsci/scsi_transport_iscsi.c: iscsi_rcv_nl_event()

- the callback checks to see that the protocol is NETLINK_GENERIC
and that the nl_pid for the socket is in taskstat's pidhash. If so, it
does a cleanup using the stored cpumask and releases the nl_pid
from the pidhash.

Sound quiet reasonable.  I am beginning to wonder whether we should do 
do the NETLINK_URELEASE in general for NETLINK_GENERIC

We can even do away with the deregister command altogether and
simply rely on this autocleanup.

I think if you may still need the register if you are going to allow
multiple sockets per listener process, no?
The other question is how do you correlate pid -> fd?

cheers,
jamal