linux-kernel - Re: [PATCH][next] drivers: hv: remove redundant assignment to pointer primary

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Date:   Wed, 15 Apr 2020 12:43:08 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        "K . Y . Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, linux-hyperv@...r.kernel.org
Subject: Re: [PATCH][next] drivers: hv: remove redundant assignment to pointer primary_channel

Colin Ian King <colin.king@...onical.com> writes:

> On 14/04/2020 17:51, Vitaly Kuznetsov wrote:
>> Colin King <colin.king@...onical.com> writes:
>> 
>>> From: Colin Ian King <colin.king@...onical.com>
>>>
>>> The pointer primary_channel is being assigned with a value that is never,
>>> The assignment is redundant and can be removed.
>>>
>>> Addresses-Coverity: ("Unused value")
>>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>>> ---
>>>  drivers/hv/channel_mgmt.c | 2 --
>>>  1 file changed, 2 deletions(-)
>>>
>>> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
>>> index ffd7fffa5f83..f7bbb8dc4b0f 100644
>>> --- a/drivers/hv/channel_mgmt.c
>>> +++ b/drivers/hv/channel_mgmt.c
>>> @@ -425,8 +425,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel)
>>>  
>>>  	if (channel->primary_channel == NULL) {
>>>  		list_del(&channel->listentry);
>>> -
>>> -		primary_channel = channel;
>>>  	} else {
>>>  		primary_channel = channel->primary_channel;
>>>  		spin_lock_irqsave(&primary_channel->lock, flags);
>> 
>> If I'm looking at the right source (5.7-rc1) it *is* beeing used:
>> 
>> 	if (channel->primary_channel == NULL) {
>> 		list_del(&channel->listentry);
>> 
>> 		primary_channel = channel;
>> 	} else {
>> 		primary_channel = channel->primary_channel;
>> 		spin_lock_irqsave(&primary_channel->lock, flags);
>> 		list_del(&channel->sc_list);
>> 		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.
>> 	 */
>> 	if (channel->affinity_policy == HV_LOCALIZED)
>> 		cpumask_clear_cpu(channel->target_cpu,
>> 				  &primary_channel->alloced_cpus_in_node);
>>                                    ^^^^^ HERE ^^^^^
>> 
>
> I was basing my change on linux-next that has removed a hunk of code:
>
> commit bcefa400900739310e8ef0cb34cbe029c404455c
> Author: Andrea Parri (Microsoft) <parri.andrea@...il.com>
> Date:   Mon Apr 6 02:15:11 2020 +0200
>
>     Drivers: hv: vmbus: Remove the unused HV_LOCALIZED channel affinity
> logic
>

Ah, please add the right 'Fixes:' tag then.

-- 
Vitaly