From: Rusty Russell <rusty@rustcorp.com.au>
To: "Martin J. Bligh" <mbligh@aracnet.com>
Cc: Nick Piggin <piggin@cyberone.com.au>, linux-kernel@vger.kernel.org
Subject: Re: New NUMA scheduler and hotplug CPU
Date: Wed, 28 Jan 2004 11:23:59 +1100 [thread overview]
Message-ID: <20040128005801.6AFD22C238@lists.samba.org> (raw)
In-Reply-To: Your message of "Tue, 27 Jan 2004 07:27:11 -0800." <368660000.1075217230@[10.10.2.4]>
In message <368660000.1075217230@[10.10.2.4]> you write:
> > Yeah, I talked it over with Rusty some on IRC. I have more of a feeling
> > why he's trying to do it that way now.
>
> BTW, Rusty - what are the locking rules for cpu_online_map under hotplug?
> Is it RCU or something? The sched domains usage of it doesn't seem to take
> any locks.
The trivial usage is to take the cpucontrol sem (down_cpucontrol()).
There's a grace period between taking the cpu offline and actually
killing it too, so for most usages RCU is sufficient.
Fortunately, I've yet to hit a case where this isn't sufficient. For
the scheduler there's an explicit "move all tasks off the CPU" call
which takes the tasklist lock and walks the tasks.
Cheers,
Rusty.
--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
next prev parent reply other threads:[~2004-01-28 0:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-01-25 23:50 New NUMA scheduler and hotplug CPU Rusty Russell
2004-01-26 8:26 ` Nick Piggin
2004-01-26 16:34 ` Martin J. Bligh
2004-01-26 23:01 ` Nick Piggin
2004-01-26 23:24 ` Martin J. Bligh
2004-01-26 23:40 ` Nick Piggin
2004-01-27 2:36 ` Rusty Russell
2004-01-27 4:38 ` Martin J. Bligh
2004-01-27 5:39 ` Nick Piggin
2004-01-27 7:19 ` Martin J. Bligh
2004-01-27 15:27 ` Martin J. Bligh
2004-01-28 0:23 ` Rusty Russell [this message]
2004-01-26 23:40 ` Andrew Theurer
2004-01-27 0:07 ` Nick Piggin
2004-01-27 2:21 ` Andrew Theurer
2004-01-27 2:40 ` Nick Piggin
2004-01-27 0:09 ` Martin J. Bligh
2004-01-27 2:19 ` Andrew Theurer
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