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

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Date:   Wed, 15 Apr 2020 15:37:52 +0100
From:   Wei Liu <wei.liu@...nel.org>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Colin Ian King <colin.king@...onical.com>,
        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

On Wed, Apr 15, 2020 at 12:43:08PM +0200, Vitaly Kuznetsov wrote:
> 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.

I don't think the Fixes tag is particularly useful in this instance.
Andrea's commit is not yet in Linus' tree. If I rebase hyper-next over
the next 2.5 months the tag is going to have a stale commit hash in it.

Wei.

> 
> -- 
> Vitaly
>