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SubjectRe: [rfc 2/3] fs, proc: Introduce the Children: line in /proc/<pid>/status
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On Friday 02 December 2011 13:10:59, Pedro Alves wrote:
> On Friday 02 December 2011 12:45:51, Cyrill Gorcunov wrote:
> > On Fri, Dec 02, 2011 at 04:43:10PM +0400, Pavel Emelyanov wrote:
> > ...
> > > >>
> > > >> Yes, I like /children file. other points seems to be pointed out by other
> > > >> reviewers.
> > > >
> > > > Any reason this is a file instead of a directory like /proc/PID/task/ ?
> > > >
> > > > $ sudo ls /proc/8167/task/
> > > > 8167 854 855 856 857 858 859
> > > > $ sudo ls /proc/8167/task/855/
> > > > attr clear_refs cpuset exe io loginuid mountinfo oom_adj pagemap sched smaps statm wchan
> > > > auxv cmdline cwd fd latency maps mounts oom_score personality schedstat stack status
> > > > cgroup comm environ fdinfo limits mem numa_maps oom_score_adj root sessionid stat syscall
> > > >
> > > > Much easier to follow the chain from the command line this way.
> > >
> > > What do you propose to put into these directories? Another directories named with
> > > children pid-s?
> > >
> >
> > Yes, I suppose additional directory/links and whatever would be just
> > noneeded overhead.
>
> /proc/8167/task/ being a directory could also be claimed
> "noneeded overhead", yet it exists, and is very useful (I use
> it a lot). Why diverge instead of being consistent?

Guess I should give an example. Here's one. While debugging
gdb stuff, I often do:

$ cat /proc/8167/task/*/status | grep State
State: S (sleeping)
State: S (sleeping)
State: S (sleeping)
State: S (sleeping)
State: S (sleeping)
State: S (sleeping)
State: S (sleeping)

If children were a directory (or "child", for
consistency with singular "task"), you could do child
things in the same natural way, like for instance:

$ ls -als /proc/8167/child/*/exe

It's like interactive pstree...

> (Note that listing /proc only shows thread group ids, but
> you can still open /proc/THREAD-ID/, so a /proc/PID/task file
> with lists of pids would have been "good enough".)

--
Pedro Alves


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