[patch] qla2xxx: fix a timeout loop

[patch] qla2xxx: fix a timeout loop

[Dan Carpenter]

After the loop we test for "if (!retries) " as a failure, but actually
the post-op here will end with retries set to -1.  I have fixed this by
using a pre-op instead.

Fixes: 7ec0effd30bb ('[SCSI] qla2xxx: Add support for ISP8044.')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/drivers/scsi/qla2xxx/qla_nx2.c b/drivers/scsi/qla2xxx/qla_nx2.c
index 007192d..66d629e 100644
--- a/drivers/scsi/qla2xxx/qla_nx2.c
+++ b/drivers/scsi/qla2xxx/qla_nx2.c
@@ -3491,7 +3491,7 @@ qla8044_poll_flash_status_reg(struct scsi_qla_host *vha)
 	int retries = QLA8044_FLASH_READ_RETRY_COUNT;
 	int ret_val = QLA_SUCCESS;
 
-	while (retries--) {
+	while (--retries) {
 		ret_val = qla8044_rd_reg_indirect(vha, QLA8044_FLASH_STATUS,
 		    &flash_status);
 		if (ret_val) {

Re: [patch] qla2xxx: fix a timeout loop

[Johannes Thumshirn]

On Wed, Dec 16, 2015 at 02:07:46PM +0300, Dan Carpenter wrote:
> After the loop we test for "if (!retries) " as a failure, but actually
> the post-op here will end with retries set to -1.  I have fixed this by
> using a pre-op instead.
> 
> Fixes: 7ec0effd30bb ('[SCSI] qla2xxx: Add support for ISP8044.')
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/drivers/scsi/qla2xxx/qla_nx2.c b/drivers/scsi/qla2xxx/qla_nx2.c
> index 007192d..66d629e 100644
> --- a/drivers/scsi/qla2xxx/qla_nx2.c
> +++ b/drivers/scsi/qla2xxx/qla_nx2.c
> @@ -3491,7 +3491,7 @@ qla8044_poll_flash_status_reg(struct scsi_qla_host *vha)
>  	int retries = QLA8044_FLASH_READ_RETRY_COUNT;
>  	int ret_val = QLA_SUCCESS;
>  
> -	while (retries--) {
> +	while (--retries) {
>  		ret_val = qla8044_rd_reg_indirect(vha, QLA8044_FLASH_STATUS,
>  		    &flash_status);
>  		if (ret_val) {
> --
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Good catch.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>

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jthumshirn@suse.de                                +49 911 74053 689
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Re: [patch] qla2xxx: fix a timeout loop

[Martin K. Petersen]

>>>>> "Dan" = Dan Carpenter <dan.carpenter@oracle.com> writes:

Dan> After the loop we test for "if (!retries) " as a failure, but
Dan> actually the post-op here will end with retries set to -1.  I have
Dan> fixed this by using a pre-op instead.

Applied to 4.4/scsi-fixes.

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [patch] qla2xxx: fix a timeout loop

[Himanshu Madhani]

Hi Dan, 


On 12/16/15, 3:07 AM, "linux-scsi-owner@vger.kernel.org on behalf of Dan
Carpenter" <linux-scsi-owner@vger.kernel.org on behalf of
dan.carpenter@oracle.com> wrote:

>After the loop we test for "if (!retries) " as a failure, but actually
>the post-op here will end with retries set to -1.  I have fixed this by
>using a pre-op instead.
>
>Fixes: 7ec0effd30bb ('[SCSI] qla2xxx: Add support for ISP8044.')
>Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>
>diff --git a/drivers/scsi/qla2xxx/qla_nx2.c
>b/drivers/scsi/qla2xxx/qla_nx2.c
>index 007192d..66d629e 100644
>--- a/drivers/scsi/qla2xxx/qla_nx2.c
>+++ b/drivers/scsi/qla2xxx/qla_nx2.c
>@@ -3491,7 +3491,7 @@ qla8044_poll_flash_status_reg(struct scsi_qla_host
>*vha)
> 	int retries = QLA8044_FLASH_READ_RETRY_COUNT;
> 	int ret_val = QLA_SUCCESS;
> 
>-	while (retries--) {
>+	while (--retries) {
> 		ret_val = qla8044_rd_reg_indirect(vha, QLA8044_FLASH_STATUS,
> 		    &flash_status);
> 		if (ret_val) {

There is flaw in this pre-decrement logic here for following 2 reasons
1. The pre-decrement reduces the total number of retries by one
2. If the retries is already Zero, then the pre-decrement would cause loop
to iterate for a very large number of times.

The correct fix for this would be to change the if(!retries) to if
(retries = -1) or if (retries < 0)

We¹ll send a follow up patch to fix this.

Thanks,
Himanshu
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Re: [patch] qla2xxx: fix a timeout loop

[Dan Carpenter]

On Wed, Dec 16, 2015 at 05:50:17PM -0500, Martin K. Petersen wrote:
> >>>>> "Dan" = Dan Carpenter <dan.carpenter@oracle.com> writes:
> 
> Dan> After the loop we test for "if (!retries) " as a failure, but
> Dan> actually the post-op here will end with retries set to -1.  I have
> Dan> fixed this by using a pre-op instead.
> 
> Applied to 4.4/scsi-fixes.
> 

The qlogic devs asked me to redo this patch but you have already applied
it.  Should I resend or redo it on top of the earlier patch.  (James's
tree was rebaseable for a day after a patch was "applied".)

regards,
dan carpenter

Re: [patch] qla2xxx: fix a timeout loop

[Martin K. Petersen]

>>>>> "Dan" = Dan Carpenter <dan.carpenter@oracle.com> writes:

Dan> The qlogic devs asked me to redo this patch but you have already
Dan> applied it.  Should I resend or redo it on top of the earlier
Dan> patch.  (James's tree was rebaseable for a day after a patch was
Dan> "applied".)

I dropped it for now.

-- 
Martin K. Petersen	Oracle Linux Engineering