Re: [PATCH 00/11] Task watchers: Introduction

[Peter Williams <pwil3058@bigpond.net.au>]

Matt Helsley wrote:
> Task watchers is a notifier chain that sends notifications to registered
> callers whenever a task forks, execs, changes its [re][ug]id, or exits.
> The goal is to keep the these paths comparatively simple while
> enabling the addition of per-task intialization, monitoring, and tear-down
> functions by existing and proposed kernel features.
> 
> The first patch adds a global atomic notifier chain, registration
> functions, and a function to invoke the callers on the chain.
> 
> Later patches:
> 
> Register a task watcher for process events, shuffle bits of process events
> functions around to reduce the code, and turn it into a module. 
> 
> Switch task watchers from an atomic to a blocking notifier chain
> 
> Register task watchers for:
> 	Audit
> 	Per Task Delay Accounting (note: not the taskstats calls)
> 	Profile
> 
> Add a per-task raw notifier chain

This feature is less useful than it could be in that it only allows a 
per-task raw notifier to be added to the current task.  For the per 
process CPU capping client that I'm writing, I'd like to be able to 
attach one of these to a task that's being forked (from the forking 
task).  Not being able to do this will force me to go to the expense of 
maintaining my own hash tables for locating my per task data.

On a related note, I can't see where the new task's notify field gets 
initialized during fork.

> 
> Add a task watcher for semundo
> 
> Switch the semundo task watcher to a per-task watcher
> 
> I've broken up the patches this way for clarity, to allow cherry-picking, and
> to help focus the discussion of any potentially controversial details.

Peter
-- 
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce