Re: New NUMA scheduler and hotplug CPU

From: Rusty Russell (rusty_at_rustcorp.com.au)
Date: 01/28/04

  • Next message: Pascal Schmidt: "Re: MO: opening for write in cdrom.c" 
    To: "Martin J. Bligh" <mbligh@aracnet.com>
Date:	Wed, 28 Jan 2004 11:23:59 +1100

    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.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
  • Next message: Pascal Schmidt: "Re: MO: opening for write in cdrom.c"

    Relevant Pages