On Thu, Jun 26, 2014 at 5:58 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> Building an allmodconfig ARM kernel, I get multiple such
> warnings because of a spinlock contained in packed structure
> in the 3w-xxxx driver:
>
> ../drivers/scsi/3w-xxxx.c: In function 'tw_chrdev_ioctl':
> ../drivers/scsi/3w-xxxx.c:1001:68: warning: mis-aligned access used for structure member [-fstrict-volatile-bitfields]
> timeout = wait_event_timeout(tw_dev->ioctl_wqueue, tw_dev->chrdev_request_id == TW_IOCTL_CHRDEV_FREE, timeout);
> ^
> ../drivers/scsi/3w-xxxx.c:1001:68: note: when a volatile object spans multiple type-sized locations, the compiler must choose between using a single mis-aligned access to preserve the volatility, or using multiple aligned accesses to avoid runtime faults; this code may fail at runtime if the hardware does not allow this access
>
> The same bug apparently was present in 3w-sas and 3w-9xxx, but has been
> fixed in the past. This patch uses the same fix by moving the pragma
> in front of the TW_Device_Extension definition, so it only covers
> hardware structures.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Adam Radford <linuxraid@xxxxxxx>
> ---
> diff --git a/drivers/scsi/3w-xxxx.h b/drivers/scsi/3w-xxxx.h
> index 49dcf03..29b0b84e 100644
> --- a/drivers/scsi/3w-xxxx.h
> +++ b/drivers/scsi/3w-xxxx.h
> @@ -392,6 +392,8 @@ typedef struct TAG_TW_Passthru
> unsigned char padding[12];
> } TW_Passthru;
>
> +#pragma pack()
> +
> typedef struct TAG_TW_Device_Extension {
> u32 base_addr;
> unsigned long *alignment_virtual_address[TW_Q_LENGTH];
> @@ -430,6 +432,4 @@ typedef struct TAG_TW_Device_Extension {
> wait_queue_head_t ioctl_wqueue;
> } TW_Device_Extension;
>
> -#pragma pack()
> -
> #endif /* _3W_XXXX_H */
>
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Arnd,
Thanks for the patch to 3w-xxxx. This looks good to me.
Acked-by: Adam Radford <aradford@xxxxxxxxx>
-Adam
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