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.
Lukasz
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