Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx> writes:
> Add hot cpu notifier to reset the request virtqueue affinity
> when doing cpu hotplug.
You need to be careful to get_online_cpus() and put_online_cpus() here,
so CPUs can't go up and down in the middle of operations.
In particular, get_online_cpus()/put_online_cpus() around calls to
virtscsi_set_affinity() (except within notifiers).
> +static int virtscsi_cpu_callback(struct notifier_block *nfb,
> + unsigned long action, void *hcpu)
> +{
> + struct virtio_scsi *vscsi = container_of(nfb, struct virtio_scsi, nb);
> + switch(action) {
> + case CPU_ONLINE:
> + case CPU_ONLINE_FROZEN:
> + case CPU_DEAD:
> + case CPU_DEAD_FROZEN:
> + virtscsi_set_affinity(vscsi, true);
> + break;
> + default:
> + break;
> + }
> + return NOTIFY_OK;
> +}
You probably want to remove affinities *before* the CPU goes down, and
restore it after the CPU comes up.
So, how about:
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
virtscsi_set_affinity(vscsi, true, -1);
break;
case CPU_DOWN_PREPARE:
virtscsi_set_affinity(vscsi, true, (unsigned long)hcpu);
break;
}
The extra argument to virtscsi_set_affinity() is to tell it to ignore a
cpu which seems online (because it's going down).
> static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
> struct virtqueue *vq)
> {
> @@ -888,6 +909,13 @@ static int __devinit virtscsi_probe(struct virtio_device *vdev)
> if (err)
> goto virtscsi_init_failed;
>
> + vscsi->nb.notifier_call = &virtscsi_cpu_callback;
> + err = register_hotcpu_notifier(&vscsi->nb);
> + if (err) {
> + pr_err("virtio_scsi: registering cpu notifier failed\n");
> + goto scsi_add_host_failed;
> + }
> +
You have to clean this up if scsi_add_host() fails, I think.
Cheers,
Rusty.
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