From mboxrd@z Thu Jan  1 00:00:00 1970
From: paulmck@linux.vnet.ibm.com (Paul E. McKenney)
Date: Mon, 9 Feb 2009 09:40:30 -0800
Subject: [ltt-dev] [RFC git tree] Userspace RCU (urcu) for Linux (repost)
In-Reply-To: <36ca99e90902090935u7fef1cb1g27303e546527e3d8@mail.gmail.com>
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	<20090206163432.GF10918@linux.vnet.ibm.com>
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	<20090209041153.GR7120@linux.vnet.ibm.com>
	<20090209045352.GA28653@Krystal>
	<20090209131653.GS7120@linux.vnet.ibm.com>
	<36ca99e90902090919r297ad4c3re2248c321b36baf8@mail.gmail.com>
	<20090209173427.GC6802@linux.vnet.ibm.com>
	<36ca99e90902090935u7fef1cb1g27303e546527e3d8@mail.gmail.com>
Message-ID: <20090209174030.GD6802@linux.vnet.ibm.com>

On Mon, Feb 09, 2009 at 06:35:38PM +0100, Bert Wesarg wrote:
> On Mon, Feb 9, 2009 at 18:34, Paul E. McKenney
> <paulmck at linux.vnet.ibm.com> wrote:
> > On Mon, Feb 09, 2009 at 06:19:45PM +0100, Bert Wesarg wrote:
> >> On Mon, Feb 9, 2009 at 14:16, Paul E. McKenney
> >> <paulmck at linux.vnet.ibm.com> wrote:
> >> > On Sun, Feb 08, 2009 at 11:53:52PM -0500, Mathieu Desnoyers wrote:
> >> >> Yes, I guess the signal is not so bad.
> >> >
> >> > Now if there were a /proc entry that listed out the tids of the
> >> > currently running threads, then it might be possible to do something,
> >> > especially for applications with many more threads than CPUs.
> >>
> >> Do you mean something like: `ls /proc/$pid/tasks/*`? Or is this not
> >> atomic enough?
> >
> > Won't that give me all the threads rather than only the ones currently
> > running?
>
> What do you mean by 'running'?

Sitting on a CPU and executing, as opposed to blocked or preempted.

It is pretty easy to scan the running tasks within the kernel, but I
don't know of an efficient way to do it from user mode.  The only way
I know of would be to cat out the /proc/$pid/tasks/*/status (IIRC)
and look for the task state.

							Thanx, Paul