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

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Date:   Mon, 3 Jun 2019 16:34:15 -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 04:25 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;
+               return;
        }

        hostdata->action = IBMVSCSI_HOST_ACTION_NONE;