Re: [PATCH 1/3] watchdog: hpwdt: add ioctl WDIOC_GETPRETIMEOUT

[Guenter Roeck]

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@xxxxxxx>
> > > ---
> > >    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