Re: [PATCH 1/1] Drivers: hv: vmbus: fix init_vp_index() for reloading hv_netvsc

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2015-08-13 at 17:07 -0700, K. Y. Srinivasan wrote:
> From: Dexuan Cui <decui@microsoft.com>
> 
> This fixes the recent commit 3b71107d73b16074afa7658f3f0fcf837aabfe24:

Which tree is this in?  upstream linus is giving me bad object on that
id.


> Drivers: hv: vmbus: Further improve CPU affiliation logic
> 
> Without the fix, reloading hv_netvsc hangs the guest.

The reason for looking for the commit id was to see if cc to stable was
necessary, is it?

James

> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
>  drivers/hv/channel_mgmt.c |   17 +++++++++++++++++
>  1 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 3ab4753..8a4105c 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -204,6 +204,8 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
>  		spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
>  		list_del(&channel->listentry);
>  		spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
> +
> +		primary_channel = channel;
>  	} else {
>  		primary_channel = channel->primary_channel;
>  		spin_lock_irqsave(&primary_channel->lock, flags);
> @@ -211,6 +213,14 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
>  		primary_channel->num_sc--;
>  		spin_unlock_irqrestore(&primary_channel->lock, flags);
>  	}
> +
> +	/*
> +	 * We need to free the bit for init_vp_index() to work in the case
> +	 * of sub-channel, when we reload drivers like hv_netvsc.
> +	 */
> +	cpumask_clear_cpu(channel->target_cpu,
> +			  &primary_channel->alloced_cpus_in_node);
> +
>  	free_channel(channel);
>  }
>  
> @@ -457,6 +467,13 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
>  			continue;
>  		}
>  
> +		/*
> +		 * NOTE: in the case of sub-channel, we clear the sub-channel
> +		 * related bit(s) in primary->alloced_cpus_in_node in
> +		 * hv_process_channel_removal(), so when we reload drivers
> +		 * like hv_netvsc in SMP guest, here we're able to re-allocate
> +		 * bit from primary->alloced_cpus_in_node.
> +		 */
>  		if (!cpumask_test_cpu(cur_cpu,
>  				&primary->alloced_cpus_in_node)) {
>  			cpumask_set_cpu(cur_cpu,