[PATCH] qla2xxx: prevent board_disable from running during EEH

[PATCH] qla2xxx: prevent board_disable from running during EEH

[Thadeu Lima de Souza Cascardo]

Commit f3ddac1918fe963bcbf8d407a3a3c0881b47248b ("[SCSI] qla2xxx:
Disable adapter when we encounter a PCI disconnect.") has introduced a
code that disables the board, releasing some resources, when reading
0xffffffff.

In case this happens when there is an EEH, this read will trigger EEH
detection and set PCI channel offline. EEH will be able to recover the
card from this state by doing a reset, so it's a better option than
simply disabling the card.

Since eeh_check_failure will mark the channel as offline before
returning the read value, in case there really was an EEH, we can simply
check for pci_channel_offline, preventing the board_disable code from
running if it's true.

Without this patch, EEH code will try to access those same resources
that board_disable will try to free. This race can cause EEH recovery to
fail.

[  504.370577] EEH: Notify device driver to resume
[  504.370580] qla2xxx [0001:07:00.0]-9002:2: The device failed to resume I/O from slot/link_reset.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Cc: <cascardo@debian.org>
Cc: <mauricfo@linux.vnet.ibm.com>
---
 drivers/scsi/qla2xxx/qla_isr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/qla2xxx/qla_isr.c b/drivers/scsi/qla2xxx/qla_isr.c
index a04a1b1..8132926 100644
--- a/drivers/scsi/qla2xxx/qla_isr.c
+++ b/drivers/scsi/qla2xxx/qla_isr.c
@@ -116,7 +116,7 @@ bool
 qla2x00_check_reg32_for_disconnect(scsi_qla_host_t *vha, uint32_t reg)
 {
 	/* Check for PCI disconnection */
-	if (reg == 0xffffffff) {
+	if (reg == 0xffffffff && !pci_channel_offline(vha->hw->pdev)) {
 		if (!test_and_set_bit(PFLG_DISCONNECTED, &vha->pci_flags) &&
 		    !test_bit(PFLG_DRIVER_REMOVING, &vha->pci_flags) &&
 		    !test_bit(PFLG_DRIVER_PROBING, &vha->pci_flags)) {
-- 
1.7.10.4

[PATCH] [RESEND] qla2xxx: prevent board_disable from running during EEH

[Mauricio Faria de Oliveira]

Commit f3ddac1918fe963bcbf8d407a3a3c0881b47248b ("[SCSI] qla2xxx:
Disable adapter when we encounter a PCI disconnect.") has introduced a
code that disables the board, releasing some resources, when reading
0xffffffff.

In case this happens when there is an EEH, this read will trigger EEH
detection and set PCI channel offline. EEH will be able to recover the
card from this state by doing a reset, so it's a better option than
simply disabling the card.

Since eeh_check_failure will mark the channel as offline before
returning the read value, in case there really was an EEH, we can simply
check for pci_channel_offline, preventing the board_disable code from
running if it's true.

Without this patch, EEH code will try to access those same resources
that board_disable will try to free. This race can cause EEH recovery to
fail.

[  504.370577] EEH: Notify device driver to resume
[  504.370580] qla2xxx [0001:07:00.0]-9002:2: The device failed to 
resume I/O from slot/link_reset.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Cc: <cascardo@debian.org>
Cc: <mauricfo@linux.vnet.ibm.com>
---
  drivers/scsi/qla2xxx/qla_isr.c |    2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/qla2xxx/qla_isr.c b/drivers/scsi/qla2xxx/qla_isr.c
index a04a1b1..8132926 100644
--- a/drivers/scsi/qla2xxx/qla_isr.c
+++ b/drivers/scsi/qla2xxx/qla_isr.c
@@ -116,7 +116,7 @@ bool
  qla2x00_check_reg32_for_disconnect(scsi_qla_host_t *vha, uint32_t reg)
  {
  	/* Check for PCI disconnection */
-	if (reg == 0xffffffff) {
+	if (reg == 0xffffffff && !pci_channel_offline(vha->hw->pdev)) {
  		if (!test_and_set_bit(PFLG_DISCONNECTED, &vha->pci_flags) &&
  		    !test_bit(PFLG_DRIVER_REMOVING, &vha->pci_flags) &&
  		    !test_bit(PFLG_DRIVER_PROBING, &vha->pci_flags)) {
-- 
1.7.10.4

Re: [PATCH] [RESEND] qla2xxx: prevent board_disable from running during EEH

[Himanshu Madhani]

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On 6/26/15, 9:33 AM, "Mauricio Faria de Oliveira"
<mauricfo@linux.vnet.ibm.com> wrote:

>Commit f3ddac1918fe963bcbf8d407a3a3c0881b47248b ("[SCSI] qla2xxx:
>Disable adapter when we encounter a PCI disconnect.") has introduced a
>code that disables the board, releasing some resources, when reading
>0xffffffff.
>
>In case this happens when there is an EEH, this read will trigger EEH
>detection and set PCI channel offline. EEH will be able to recover the
>card from this state by doing a reset, so it's a better option than
>simply disabling the card.
>
>Since eeh_check_failure will mark the channel as offline before
>returning the read value, in case there really was an EEH, we can simply
>check for pci_channel_offline, preventing the board_disable code from
>running if it's true.
>
>Without this patch, EEH code will try to access those same resources
>that board_disable will try to free. This race can cause EEH recovery to
>fail.
>
>[  504.370577] EEH: Notify device driver to resume
>[  504.370580] qla2xxx [0001:07:00.0]-9002:2: The device failed to
>resume I/O from slot/link_reset.
>
>Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
>Cc: <cascardo@debian.org>
>Cc: <mauricfo@linux.vnet.ibm.com>
>---
>  drivers/scsi/qla2xxx/qla_isr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/scsi/qla2xxx/qla_isr.c
>b/drivers/scsi/qla2xxx/qla_isr.c
>index a04a1b1..8132926 100644
>--- a/drivers/scsi/qla2xxx/qla_isr.c
>+++ b/drivers/scsi/qla2xxx/qla_isr.c
>@@ -116,7 +116,7 @@ bool
>  qla2x00_check_reg32_for_disconnect(scsi_qla_host_t *vha, uint32_t reg)
>  {
>  	/* Check for PCI disconnection */
>-	if (reg == 0xffffffff) {
>+	if (reg == 0xffffffff && !pci_channel_offline(vha->hw->pdev)) {
>  		if (!test_and_set_bit(PFLG_DISCONNECTED, &vha->pci_flags) &&
>  		    !test_bit(PFLG_DRIVER_REMOVING, &vha->pci_flags) &&
>  		    !test_bit(PFLG_DRIVER_PROBING, &vha->pci_flags)) {
>-- 
>1.7.10.4
>
>

Looks good. 

Acked-by: Himanshu Madhani <himanshu.madhani@qlogic.com>

>
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Re: [PATCH] [RESEND] qla2xxx: prevent board_disable from running during EEH

[Joe Lawrence]

On 06/26/2015 12:33 PM, Mauricio Faria de Oliveira wrote:
> Commit f3ddac1918fe963bcbf8d407a3a3c0881b47248b ("[SCSI] qla2xxx:
> Disable adapter when we encounter a PCI disconnect.") has introduced a
> code that disables the board, releasing some resources, when reading
> 0xffffffff.
> 
> In case this happens when there is an EEH, this read will trigger EEH
> detection and set PCI channel offline. EEH will be able to recover the
> card from this state by doing a reset, so it's a better option than
> simply disabling the card.
> 
> Since eeh_check_failure will mark the channel as offline before
> returning the read value, in case there really was an EEH, we can simply
> check for pci_channel_offline, preventing the board_disable code from
> running if it's true.
> 
> Without this patch, EEH code will try to access those same resources
> that board_disable will try to free. This race can cause EEH recovery to
> fail.
> 
> [  504.370577] EEH: Notify device driver to resume
> [  504.370580] qla2xxx [0001:07:00.0]-9002:2: The device failed to
> resume I/O from slot/link_reset.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
> Cc: <cascardo@debian.org>
> Cc: <mauricfo@linux.vnet.ibm.com>
> ---
>  drivers/scsi/qla2xxx/qla_isr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/qla2xxx/qla_isr.c
> b/drivers/scsi/qla2xxx/qla_isr.c
> index a04a1b1..8132926 100644
> --- a/drivers/scsi/qla2xxx/qla_isr.c
> +++ b/drivers/scsi/qla2xxx/qla_isr.c
> @@ -116,7 +116,7 @@ bool
>  qla2x00_check_reg32_for_disconnect(scsi_qla_host_t *vha, uint32_t reg)
>  {
>      /* Check for PCI disconnection */
> -    if (reg == 0xffffffff) {
> +    if (reg == 0xffffffff && !pci_channel_offline(vha->hw->pdev)) {
>          if (!test_and_set_bit(PFLG_DISCONNECTED, &vha->pci_flags) &&
>              !test_bit(PFLG_DRIVER_REMOVING, &vha->pci_flags) &&
>              !test_bit(PFLG_DRIVER_PROBING, &vha->pci_flags)) {

Hi Mauricio,

Re: signed-off-by chain -- I believe if you are (re)sending another
person's patch, you will need a:  "From: Thadeu Lima de Souza Cascardo
<cascardo@linux.vnet.ibm.com>"  tag at the top of the message body to
retain original authorship and then your own:  "Signed-off-by: Mauricio
Faria de Oliveira <mauricfo@linux.vnet.ibm.com>" tag below Thadeu's
since the patch has passed through you.

Re: the patch -- I did some work last year to harden board_disable
against various races, but without having EEH hardware available, I was
uncertain about EEH behavior.  For example:

pci_read
   EEH -> marks channel offline
pci_read returns ~0

When do the EEH error handler callbacks run?

Thanks,

-- Joe