On 06/02/2019 03:15 AM, Michael Ellerman wrote:
> Hi Nathan,
>
> Nathan Chancellor <natechancellor@xxxxxxxxx> writes:
>> 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 so that the atomic_set and dev_err statement don't
>> trigger for the cases that just break.
>>
>> Fixes: 035a3c4046b5 ("scsi: ibmvscsi: redo driver work thread to use enum action states")
>> Link: https://github.com/ClangBuiltLinux/linux/issues/502
>> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
>> ---
>> drivers/scsi/ibmvscsi/ibmvscsi.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
>> index 727c31dc11a0..6714d8043e62 100644
>> --- a/drivers/scsi/ibmvscsi/ibmvscsi.c
>> +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
>> @@ -2118,7 +2118,7 @@ static unsigned long ibmvscsi_get_desired_dma(struct vio_dev *vdev)
>> static void ibmvscsi_do_work(struct ibmvscsi_host_data *hostdata)
>> {
>> unsigned long flags;
>> - int rc;
>> + int rc = 0;
>> char *action = "reset";
>>
>> spin_lock_irqsave(hostdata->host->host_lock, flags);
>
> It's always preferable IMHO to keep any initialisation as localised as
> possible, so that the compiler can continue to warn about uninitialised
> usages elsewhere. In this case that would mean doing the rc = 0 in the
> switch, something like:
>
> diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
> index 727c31dc11a0..7ee5755cf636 100644
> --- a/drivers/scsi/ibmvscsi/ibmvscsi.c
> +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
> @@ -2123,9 +2123,6 @@ 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:
> - break;
> case IBMVSCSI_HOST_ACTION_RESET:
> spin_unlock_irqrestore(hostdata->host->host_lock, flags);
> rc = ibmvscsi_reset_crq_queue(&hostdata->queue, hostdata);
> @@ -2142,7 +2139,10 @@ 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:
> + case IBMVSCSI_HOST_ACTION_UNBLOCK:
> default:
> + rc = 0;
> break;
> }
>
>
> But then that makes me wonder if that's actually correct?
>
> If we get an action that we don't recognise should we just throw it away
> like that? (by doing hostdata->action = IBMVSCSI_HOST_ACTION_NONE). Tyrel?
On initial pass I was ok with this, but after thinking on it I think it is more
subtle.
The right approach is to set rc = 0 for HOST_ACTION_UNBLOCK as we want to fall
through. For HOST_ACTION_NONE and default we need to return directly from the
function.
-Tyrel
>
> cheers
>
