linux-kernel - Re: [PATCH v2] scsi: ibmvscsi: Don't use rc uninitialized in ibmvscsi_do

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Date:   Mon, 3 Jun 2019 16:35:52 -0700
From:   Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Tyrel Datwyler <tyreld@...ux.ibm.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     linux-scsi@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v2] scsi: ibmvscsi: Don't use rc uninitialized in
 ibmvscsi_do_work

On 06/03/2019 04:34 PM, Tyrel Datwyler wrote:
> On 06/03/2019 04:25 PM, Tyrel Datwyler wrote:
>> On 06/03/2019 03:19 PM, Nathan Chancellor wrote:
>>> clang warns:
>>>
>>> drivers/scsi/ibmvscsi/ibmvscsi.c:2126:7: warning: variable 'rc' is used
>>> uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
>>>         case IBMVSCSI_HOST_ACTION_NONE:
>>>              ^~~~~~~~~~~~~~~~~~~~~~~~~
>>> drivers/scsi/ibmvscsi/ibmvscsi.c:2151:6: note: uninitialized use occurs
>>> here
>>>         if (rc) {
>>>             ^~
>>>
>>> Initialize rc to zero in the case statements that clang mentions so that
>>> the atomic_set and dev_err statement don't trigger for them.
>>>
>>> Fixes: 035a3c4046b5 ("scsi: ibmvscsi: redo driver work thread to use enum action states")
>>> Link: https://github.com/ClangBuiltLinux/linux/issues/502
>>> Suggested-by: Michael Ellerman <mpe@...erman.id.au>
>>> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
>>
>> Acked-by: Tyrel Datwyler <tyreld@...ux.ibm.com>
>>
> 
> On second thought NACK. See my response to Michael earlier in the thread.
> 
> I think this is the better solution:
> 
> diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
> index 727c31dc11a0..c3cf05dd8733 100644
> --- a/drivers/scsi/ibmvscsi/ibmvscsi.c
> +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
> @@ -2123,8 +2123,8 @@ static void ibmvscsi_do_work(struct ibmvscsi_host_data
> *hostdata)
> 
>         spin_lock_irqsave(hostdata->host->host_lock, flags);
>         switch (hostdata->action) {
> -       case IBMVSCSI_HOST_ACTION_NONE:
>         case IBMVSCSI_HOST_ACTION_UNBLOCK:
> +               rc = 0;
>                 break;
>         case IBMVSCSI_HOST_ACTION_RESET:
>                 spin_unlock_irqrestore(hostdata->host->host_lock, flags);
> @@ -2142,8 +2142,9 @@ static void ibmvscsi_do_work(struct ibmvscsi_host_data
> *hostdata)
>                 if (!rc)
>                         rc = ibmvscsi_send_crq(hostdata, 0xC001000000000000LL, 0);
>                 break;
> +       case IBMVSCSI_HOST_ACTION_NONE:
>         default:
> -               break;

Need a spin_unlock_irqrestore() here before the return.

-Tyrel

> +               return;
>         }
> 
>         hostdata->action = IBMVSCSI_HOST_ACTION_NONE;
>