On 17.01.2014 14:55, Dorau, Lukasz wrote:
> On Friday, January 17, 2014 2:37 PM Dorau, Lukasz <lukasz.do...@intel.com>
> wrote:
>>
>> Hi
>>
>> My story is very simply...
>> I applied the following patch:
>>
>> diff --git a/drivers/scsi/isci/init.c b/drivers/scsi/isci/init.c
>> --- a/drivers/scsi/isci/init.c
>> +++ b/drivers/scsi/isci/init.c
>> @@ -698,8 +698,11 @@ static int isci_pci_probe(struct pci_dev *pdev, const
>> struct
>> pci_device_id *id)
>> if (err)
>> goto err_host_alloc;
>>
>> - for_each_isci_host(i, isci_host, pdev)
>> + for_each_isci_host(i, isci_host, pdev) {
>> + pr_err("(%d < %d) == %d\n",\
>> + i, SCI_MAX_CONTROLLERS, (i < SCI_MAX_CONTROLLERS));
>> scsi_scan_host(to_shost(isci_host));
>> + }
>>
>> return 0;
>>
>> --
>> 1.8.3.1
>>
>> Then I issued the command 'modprobe isci' on platform with two SCU
>> controllers
>> (Patsburg D or T chipset)
>> and received the following, very strange, output:
>>
>> (0 < 2) == 1
>> (1 < 2) == 1
>> (2 < 2) == 1
>>
>> Can anyone explain why (2 < 2) is true? Is it a gcc bug?
>>
>> (The kernel was compiled using gcc version 4.8.2.)
>>
>
> Some additional information:
>
> The loop 'for' in macro ' for_each_isci_host ' defined as
> (drivers/scsi/isci/host.h:313):
>
> #define for_each_isci_host(id, ihost, pdev) \
> for (id = 0, ihost = to_pci_info(pdev)->hosts[id]; \
> id < ARRAY_SIZE(to_pci_info(pdev)->hosts) && ihost; \
> ihost = to_pci_info(pdev)->hosts[++id])
>
> should be executed only for i = 0 and 1, because:
> ARRAY_SIZE(to_pci_info(pdev)->hosts) = SCI_MAX_CONTROLLERS = 2
>
> but it was executed also for i=2 regardless the above loop's end condition.
to_pci_info() can return NULL in dev_get_drvdata(). The use of
ARRAY_SIZE() is inappropriate.
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) +
__must_be_array(arr))
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
I would say that this was supposed to trigger a build error but it
didn't and added 1 to the loop end condition.
Can you test putting SCI_MAX_CONTROLLERS to the loop end condition, please?
Cheers,
Sebastian
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