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SubjectRe: [RFC PATCH v2 11/14] x86/watchdog/hardlockup: Add an HPET-based hardlockup detector
On Fri, Apr 05, 2019 at 04:12:56PM +0000, Suthikulpanit, Suravee wrote:
> Hi Neri,

Hi Suravee,

Many thanks for testing the patches!
>
> While trying out this patch series, I found that it does not work when the HPET timer
> is in periodic mode.

I should have tested this better. I'll double check my setup.
>
> On 2/27/19 11:05 PM, Ricardo Neri wrote:
> > ......
> > diff --git a/arch/x86/kernel/watchdog_hld_hpet.c b/arch/x86/kernel/watchdog_hld_hpet.c
> > new file mode 100644
> > index 000000000000..cfa284da4bf6
> > --- /dev/null
> > +++ b/arch/x86/kernel/watchdog_hld_hpet.c
> > @@ -0,0 +1,405 @@
> > .....
> > +
> > +/**
> > + * set_comparator() - Update the comparator in an HPET timer instance
> > + * @hdata: A data structure with the timer instance to update
> > + * @cmp: The value to write in the in the comparator registere
> > + *
> > + * Returns:
> > + *
> > + * None
> > + */
> > +static inline void set_comparator(struct hpet_hld_data *hdata,
> > + unsigned long cmp)
> > +{
> > + hpet_writeq(cmp, HPET_Tn_CMP(hdata->num));
> > +}
> > +
> > +/**
> > + * kick_timer() - Reprogram timer to expire in the future
> > + * @hdata: A data structure with the timer instance to update
> > + * @force: Force reprogram. Useful enabling or re-enabling detector.
> > + *
> > + * Reprogram the timer to expire within watchdog_thresh seconds in the future.
> > + *
> > + * Returns:
> > + *
> > + * None
> > + */
> > +static void kick_timer(struct hpet_hld_data *hdata, bool force)
> > +{
> > + bool kick_needed = force || !(hdata->flags & HPET_DEV_PERI_CAP);
> > + unsigned long new_compare, count;
> > +
> > + /*
> > + * Update the comparator in increments of watch_thresh seconds relative
> > + * to the current count. Since watch_thresh is given in seconds, we
> > + * are able to update the comparator before the counter reaches such new
> > + * value.
> > + *
> > + * Let it wrap around if needed.
> > + */
> > +
> > + if (kick_needed) {
> > + count = get_count();
> > +
> > + new_compare = count + watchdog_thresh * hdata->ticks_per_second;
> > +
> > + set_comparator(hdata, new_compare);
> > + }
> > +}
> It turns out that the set_comparator() does not seem to support periodic mode,
> in which it should have been setting the accumulator/period via the comparator register.
>
> Instead, what if we re-factor the code in the arch/x86/kernel/hpet.c:hpet_set_periodic()
> to hpet_set_comparator(). Then we can also reuse it in the arch/x86/kernel/watchdog_hld_pet.c:
> kick_timer() as shown below.
>
> With these changes, I can test the series on AMD systems, and see all cores
> in /proc/interrupts are receiving NMI interrupts.

These changes look OK to me. Thanks! I'll incorporate them in my next version.

>
> Regards,
> Suravee
>
>
> diff --git a/arch/x86/include/asm/hpet.h b/arch/x86/include/asm/hpet.h
> index 0976334..f30957f 100644
> --- a/arch/x86/include/asm/hpet.h
> +++ b/arch/x86/include/asm/hpet.h
> @@ -115,6 +115,7 @@ extern int hpet_rtc_timer_init(void);
> extern irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id);
> extern int hpet_register_irq_handler(rtc_irq_handler handler);
> extern void hpet_unregister_irq_handler(rtc_irq_handler handler);
> +extern void hpet_set_comparator(int num, unsigned int cmp, unsigned int period);
>
> #endif /* CONFIG_HPET_EMULATE_RTC */
>
> diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
> index 03b05dae..f3b2351 100644
> --- a/arch/x86/kernel/hpet.c
> +++ b/arch/x86/kernel/hpet.c
> @@ -328,6 +328,41 @@ static void hpet_legacy_clockevent_register(void)
> printk(KERN_DEBUG "hpet clockevent registered\n");
> }
>
> +/*
> + * hpet_set_comparator() - Helper function for setting comparator register
> + * @num: The timer ID
> + * @cmp: The value to be written to the comparator/accumulator
> + * @period: The value to be written to the period (0 = oneshot mode)
> + *
> + * Helper function for updating comparator, accumulator and period values.
> + *
> + * In periodic mode, HPET needs HPET_TN_SETVAL to be set before writing
> + * to the Tn_CMP to update the accumulator. Then, HPET needs a second
> + * write (with HPET_TN_SETVAL cleared) to Tn_CMP to set the period.
> + * The HPET_TN_SETVAL bit is automatically cleared after the first write.
> + *
> + * For one-shot mode, HPET_TN_SETVAL does not need to be set.
> + *
> + * See the following documents:
> + * - Intel IA-PC HPET (High Precision Event Timers) Specification
> + * - AMD-8111 HyperTransport I/O Hub Data Sheet, Publication # 24674
> + */
> +void hpet_set_comparator(int num, unsigned int cmp, unsigned int period)
> +{
> + if (period) {
> + unsigned int v = hpet_readl(HPET_Tn_CFG(num));
> + hpet_writel(v | HPET_TN_SETVAL, HPET_Tn_CFG(num));
> + }
> +
> + hpet_writel(cmp, HPET_Tn_CMP(num));
> + if (!period)
> + return;
> +
> + udelay(1);
> + hpet_writel(period, HPET_Tn_CMP(num));
> +}
> +EXPORT_SYMBOL_GPL(hpet_set_comparator);
> +
> static int hpet_set_periodic(struct clock_event_device *evt, int timer)
> {
> unsigned int cfg, cmp, now;
> @@ -339,19 +374,11 @@ static int hpet_set_periodic(struct clock_event_device *evt, int timer)
> now = hpet_readl(HPET_COUNTER);
> cmp = now + (unsigned int)delta;
> cfg = hpet_readl(HPET_Tn_CFG(timer));
> - cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
> - HPET_TN_32BIT;
> + cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_32BIT;
> hpet_writel(cfg, HPET_Tn_CFG(timer));
> - hpet_writel(cmp, HPET_Tn_CMP(timer));
> - udelay(1);
> - /*
> - * HPET on AMD 81xx needs a second write (with HPET_TN_SETVAL
> - * cleared) to T0_CMP to set the period. The HPET_TN_SETVAL
> - * bit is automatically cleared after the first write.
> - * (See AMD-8111 HyperTransport I/O Hub Data Sheet,
> - * Publication # 24674)
> - */
> - hpet_writel((unsigned int)delta, HPET_Tn_CMP(timer));
> +
> + hpet_set_comparator(timer, cmp, (unsigned int)delta);
> +
> hpet_start_counter();
> hpet_print_config();
>
> diff --git a/arch/x86/kernel/watchdog_hld_hpet.c b/arch/x86/kernel/watchdog_hld_hpet.c
> index 4402def..de33c50 100644
> --- a/arch/x86/kernel/watchdog_hld_hpet.c
> +++ b/arch/x86/kernel/watchdog_hld_hpet.c
> @@ -35,21 +35,6 @@ static inline unsigned long get_count(void)
> }
>
> /**
> - * set_comparator() - Update the comparator in an HPET timer instance
> - * @hdata: A data structure with the timer instance to update
> - * @cmp: The value to write in the in the comparator registere
> - *
> - * Returns:
> - *
> - * None
> - */
> -static inline void set_comparator(struct hpet_hld_data *hdata,
> - unsigned long cmp)
> -{
> - hpet_writeq(cmp, HPET_Tn_CMP(hdata->num));
> -}
> -
> -/**
> * kick_timer() - Reprogram timer to expire in the future
> * @hdata: A data structure with the timer instance to update
> * @force: Force reprogram. Useful enabling or re-enabling detector.
> @@ -68,7 +53,7 @@ static inline void set_comparator(struct hpet_hld_data *hdata,
> static void kick_timer(struct hpet_hld_data *hdata, bool force)
> {
> bool kick_needed = force || !(hdata->flags & HPET_DEV_PERI_CAP);
> - unsigned long tsc_curr, tsc_delta, new_compare, count;
> + unsigned long tsc_curr, tsc_delta, new_compare, count, period = 0;
>
> /* Start obtaining the current TSC and HPET counts. */
> tsc_curr = rdtsc();
> @@ -81,6 +66,9 @@ static void kick_timer(struct hpet_hld_data *hdata, bool force)
> hdata->tsc_next = tsc_curr + tsc_delta;
> hdata->tsc_next_error = tsc_delta >> 6;
>
> + if (!kick_needed)
> + return;
> +
> /*
> * Update the comparator in increments of watch_thresh seconds relative
> * to the current count. Since watch_thresh is given in seconds, we
> @@ -89,12 +77,11 @@ static void kick_timer(struct hpet_hld_data *hdata, bool force)
> *
> * Let it wrap around if needed.
> */
> + if (hdata->flags & HPET_DEV_PERI_CAP)
> + period = watchdog_thresh * hdata->ticks_per_second;
>
> - if (kick_needed) {
> - new_compare = count + watchdog_thresh * hdata->ticks_per_second;
> -
> - set_comparator(hdata, new_compare);
> - }
> + new_compare = count + period;
> + hpet_set_comparator(hdata->num, new_compare, period);
> }
>
> /**
> --
> 2.7.4

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