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SubjectRe: [PATCH 1/3] watchdog: hpwdt: add ioctl WDIOC_GETPRETIMEOUT
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On 10/21/2017 06:41 PM, Jerry Hoemann wrote:
> On Fri, Oct 20, 2017 at 07:25:20PM -0700, Guenter Roeck wrote:
>> On 10/20/2017 03:54 PM, Jerry Hoemann wrote:
>>> Add support for WDIOC_GETPRETIMEOUT ioctl so that user applications
>>> can determine when the NMI should arrive.
>>>
>>> Signed-off-by: Jerry Hoemann <jerry.hoemann@hpe.com>
>>> ---
>>> drivers/watchdog/hpwdt.c | 7 +++++++
>>> 1 file changed, 7 insertions(+)
>>>
>>> diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
>>> index 67fbe35..ef54b03 100644
>>> --- a/drivers/watchdog/hpwdt.c
>>> +++ b/drivers/watchdog/hpwdt.c
>>> @@ -50,6 +50,7 @@
>>> static bool nowayout = WATCHDOG_NOWAYOUT;
>>> static char expect_release;
>>> static unsigned long hpwdt_is_open;
>>> +static const int pretimeout = 9;
>>> static void __iomem *pci_mem_addr; /* the PCI-memory address */
>>> static unsigned long __iomem *hpwdt_timer_reg;
>>> @@ -622,6 +623,12 @@ static long hpwdt_ioctl(struct file *file, unsigned int cmd,
>>> }
>>> break;
>>> + case WDIOC_GETPRETIMEOUT:
>>> + ret = copy_to_user(argp, &pretimeout, sizeof(pretimeout));
>>> + if (ret)
>>> + ret = -EFAULT;
>>> + break;
>>> +
>>> case WDIOC_SETTIMEOUT:
>>> ret = get_user(new_margin, p);
>>> if (ret)
>>>
>>
>> Can you please convert the driver to use the watchdog subsystem instead ?
>> If there are still improvements needed afterwards, they can still be
>> implemented, but we really should not make improvements which are
>> already supported by the watchdog core.
>
> I will look into converting the driver, but would like to get this
> fix in independently.
>

I don't see this patch as a fix. It adds functionality. the other two patches
are fixes and should come first.

> SuSE brought https://bugzilla.novell.com/show_bug.cgi?id=1042933
> to my attention earlier this summer. The submitter was trying to
> develop a watchdog test where the ping rate was set to be the
> Timeout/2.
>
> The test worked fine until (Timeout/2) < PreTimeout. At this point
> an NMI would be delivered to the system before the test could refresh
> the timer.
>
Yes, but I don't think that is fixed with this patch. That would be patch 3/3, no ?

Guenter

> I came to the view that a watchdog that implements a pre-timeout NMI
> where the value of the pre-timeout is not known programmatically as having
> a defect.
>
> This problem has been around a long time and we could live with it, but
> figured while I was in fixing other problems, I'd fix this one as well.
>
> Thanks
>

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