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SubjectRe: [PATCH] keep rd->online and cpu_online_map in sync
On Mon, Mar 10, 2008 at 09:39:34AM -0400, Gregory Haskins wrote:
> keep rd->online and cpu_online_map in sync
>
> It is possible to allow the root-domain cache of online cpus to
> become out of sync with the global cpu_online_map. This is because we
> currently trigger removal of cpus too early in the notifier chain.
> Other DOWN_PREPARE handlers may in fact run and reconfigure the
> root-domain topology, thereby stomping on our own offline handling.
>
> The end result is that rd->online may become out of sync with
> cpu_online_map, which results in potential task misrouting.
>
> So change the offline handling to be more tightly coupled with the
> global offline process by triggering on CPU_DYING intead of
> CPU_DOWN_PREPARE.
>
> Signed-off-by: Gregory Haskins <ghaskins@novell.com>
> ---
>
> kernel/sched.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 52b9867..a616fa1 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -5881,7 +5881,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
> spin_unlock_irq(&rq->lock);
> break;
>
> - case CPU_DOWN_PREPARE:
> + case CPU_DYING:

Don't we need to take care of CPU_DYING_FROZEN aswell?

> /* Update our root-domain */
> rq = cpu_rq(cpu);
> spin_lock_irqsave(&rq->lock, flags);
>


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