Re: [patch] kernel events layer

[Andrew Morton <akpm@osdl.org>]

Robert Love <rml@ximian.com> wrote:
>
> Andrew, et al,
> 
> OK, Kernel Summit and my OLS talk are over, so here are the goods.
> 
> Following patch implements the kernel events layer, which is a simple
> wrapper around netlink to allow asynchronous communication from the
> kernel to user-space of events, errors, logging, and so on.
> 
> Current intention is to hook the kernel via this interface into D-BUS,
> although the patch is intended to be agnostic to any of that and policy
> free.
> 
> D-BUS can be found here:
> 
> 	http://dbus.freedesktop.org/
> 
> Other user-space utilities (including code to utilize this) can be found
> here:
> 
> 	http://vrfy.org/projects/kdbusd/
> 
> This patch only implements a single event, processor temperature
> detection.  Other useful events include md sync, filesystem mount,
> driver errors, etc.  We can add those later, on a case-by-case basis.  I
> would like to be more careful with adding events than we are with adding
> printk's, with some aim toward a stable interface.

OK.  Can you give us a ballpark estimate of how many send_kmessage() calls
we're likely to have in two years time?

> Usage of the new interface is simple:
> 
> 	send_kmessage(group, interface, message, ...)
> 
> Credit to Arjan for the initial implementation, Kay Sievers for some
> updates, and the netlink code.

- The GFP_ATOMIC page allocation is unfortunate.  Please pass in the
  gfp_flags, or change it to GFP_KERNEL and provide a separate
  send_kmessage_atomic()?

- Methinks the kernel won't build if the user set CONFIG_NETLINK_DEV=n

- When fixing that up, please add CONFIG_KERNEL_EVENTS or whatever,
  provide the appropriate do-nothing stubs if it's disabled.  For the tiny
  systems.

- send_kmessage() is racy against kmessage_exit().  I'm not sure that's
  worth fixing - if you agree then it would set minds at ease to simply
  remove kmessage_exit().

- This code will never work as a module, so why include the
  MODULE_AUTHOR/DESCRIPTION/etc?

- What led to the decision to export send_kmessage() to only GPL modules?