[PATCH 1/3] clocksource: exynos_mct: Fix stall after CPU hotplugging
Krzysztof Kozlowski
k.kozlowski at samsung.com
Wed Apr 16 01:51:03 PDT 2014
On wto, 2014-04-15 at 18:20 +0200, Thomas Gleixner wrote:
> B1;3202;0cOn Tue, 15 Apr 2014, Krzysztof Kozlowski wrote:
> > On wto, 2014-04-15 at 17:20 +0200, Thomas Gleixner wrote:
> > > On Tue, 15 Apr 2014, Krzysztof Kozlowski wrote:
> > >
> > > > On wto, 2014-04-15 at 14:28 +0200, Daniel Lezcano wrote:
> > > > > On 04/15/2014 11:34 AM, Krzysztof Kozlowski wrote:
> > > > > > On pią, 2014-03-28 at 14:06 +0100, Krzysztof Kozlowski wrote:
> > > > > >> Fix stall after hotplugging CPU1. Affected are SoCs where Multi Core Timer
> > > > > >> interrupts are shared (SPI), e.g. Exynos 4210. The stall was a result of
> > > > > >> starting the CPU1 local timer not in L1 timer but in L0 (which is used
> > > > > >> by CPU0).
> > > > > >
> > > > > > Hi,
> > > > > >
> > > > > > Do you have any comments on these 3 patches? They fix the CPU stall on
> > > > > > Exynos4210 and also on Exynos3250 (Chanwoo Choi sent patches for it
> > > > > > recently).
> > > > >
> > > > > You describe this issue as impacting different SoC not only the exynos,
> > > > > right ?
> > > > >
> > > > > Do you know what other SoCs are impacted by this ?
> > > >
> > > > No, affected are only Exynos SoC-s. It was confirmed on Exynos4210
> > > > (Trats board) and Exynos3250 (new SoC, patches for it were recently
> > > > posted by Chanwoo).
> > > >
> > > > Other Exynos SoC-s where MCT local timers use shared interrupts (SPI)
> > > > can also be affected. Candidates are Exynos 5250 and 5420 but I haven't
> > > > tested them.
> > > >
> > > > > I guess this issue is not reproducible just with the line below, we need
> > > > > a timer to expire right at the moment CPU1 is hotplugged, right ?
> > > >
> > > > Right. The timer must fire in short time between enabling local timer
> > > > for CPU1 and setting the affinity for IRQ.
> > >
> > > Why do you set the affinity in the CPU_ONLINE hotplug callback and not
> > > right away when the interrupt is requested?
> >
> > Hi,
> >
> > I think the problem in such code is in GIC. The gic_set_affinity() uses
> > cpu_online_mask:
> > unsigned int cpu = cpumask_any_and(mask_val, cpu_online_mask);
> > In that time this CPU is not present in that mask so -EINVAL would be
> > returned.
>
> Hmm, indeed. Stupid me.
>
> Here is a complete solution to the problem. We really want the drivers
> to be fast and clean and not work around such issues.
>
> I'm quite happy that I kept the 'force' argument of set_affinity
> callbacks. I knew that I'd need it at some point.
>
> So with the flag set we can disable the online mask check and force
> the interrupt to the proper cpu.
Thanks for the solution.
I tested your patch on Exynos 3250 and it is still not sufficient. After
hotplugging CPU1 ~10 times the stall happens (set_next_event is called
on wrong CPU).
The patch 3/3 ("clocksource: exynos_mct: Fix too early ISR fire up on
wrong CPU") is needed as the clockevents_config_and_register should be
called a little later.
Do you have rest of patches (2/3 and 3/3) or should I resend them?
And one minor nit in your patch: 'cpu' local variable in
exynos4_mct_cpu_notify() is no longer used so it can be removed.
Best regards,
Krzysztof
> Thanks,
>
> tglx
>
> Index: linux-2.6/drivers/clocksource/exynos_mct.c
> ===================================================================
> --- linux-2.6.orig/drivers/clocksource/exynos_mct.c
> +++ linux-2.6/drivers/clocksource/exynos_mct.c
> @@ -430,6 +430,7 @@ static int exynos4_local_timer_setup(str
> evt->irq);
> return -EIO;
> }
> + irq_force_affinity(mct_irqs[MCT_L0_IRQ + cpu], cpumask_of(cpu));
> } else {
> enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0);
> }
> @@ -461,12 +462,6 @@ static int exynos4_mct_cpu_notify(struct
> mevt = this_cpu_ptr(&percpu_mct_tick);
> exynos4_local_timer_setup(&mevt->evt);
> break;
> - case CPU_ONLINE:
> - cpu = (unsigned long)hcpu;
> - if (mct_int_type == MCT_INT_SPI)
> - irq_set_affinity(mct_irqs[MCT_L0_IRQ + cpu],
> - cpumask_of(cpu));
> - break;
> case CPU_DYING:
> mevt = this_cpu_ptr(&percpu_mct_tick);
> exynos4_local_timer_stop(&mevt->evt);
> Index: linux-2.6/drivers/irqchip/irq-gic.c
> ===================================================================
> --- linux-2.6.orig/drivers/irqchip/irq-gic.c
> +++ linux-2.6/drivers/irqchip/irq-gic.c
> @@ -246,10 +246,14 @@ static int gic_set_affinity(struct irq_d
> bool force)
> {
> void __iomem *reg = gic_dist_base(d) + GIC_DIST_TARGET + (gic_irq(d) & ~3);
> - unsigned int shift = (gic_irq(d) % 4) * 8;
> - unsigned int cpu = cpumask_any_and(mask_val, cpu_online_mask);
> + unsigned int cpu, shift = (gic_irq(d) % 4) * 8;
> u32 val, mask, bit;
>
> + if (!force)
> + cpu = cpumask_any_and(mask_val, cpu_online_mask);
> + else
> + cpu = cpumask_first(mask_val);
> +
> if (cpu >= NR_GIC_CPU_IF || cpu >= nr_cpu_ids)
> return -EINVAL;
>
> Index: linux-2.6/include/linux/interrupt.h
> ===================================================================
> --- linux-2.6.orig/include/linux/interrupt.h
> +++ linux-2.6/include/linux/interrupt.h
> @@ -204,6 +204,7 @@ static inline int check_wakeup_irqs(void
> extern cpumask_var_t irq_default_affinity;
>
> extern int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask);
> +extern int irq_force_affinity(unsigned int irq, const struct cpumask *cpumask);
> extern int irq_can_set_affinity(unsigned int irq);
> extern int irq_select_affinity(unsigned int irq);
>
> Index: linux-2.6/kernel/irq/manage.c
> ===================================================================
> --- linux-2.6.orig/kernel/irq/manage.c
> +++ linux-2.6/kernel/irq/manage.c
> @@ -180,7 +180,7 @@ int irq_do_set_affinity(struct irq_data
> struct irq_chip *chip = irq_data_get_irq_chip(data);
> int ret;
>
> - ret = chip->irq_set_affinity(data, mask, false);
> + ret = chip->irq_set_affinity(data, mask, force);
> switch (ret) {
> case IRQ_SET_MASK_OK:
> cpumask_copy(data->affinity, mask);
> @@ -192,7 +192,8 @@ int irq_do_set_affinity(struct irq_data
> return ret;
> }
>
> -int __irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask)
> +static int irq_do_set_affinity_locked(struct irq_data *data,
> + const struct cpumask *mask, bool force)
> {
> struct irq_chip *chip = irq_data_get_irq_chip(data);
> struct irq_desc *desc = irq_data_to_desc(data);
> @@ -202,7 +203,7 @@ int __irq_set_affinity_locked(struct irq
> return -EINVAL;
>
> if (irq_can_move_pcntxt(data)) {
> - ret = irq_do_set_affinity(data, mask, false);
> + ret = irq_do_set_affinity(data, mask, force);
> } else {
> irqd_set_move_pending(data);
> irq_copy_pending(desc, mask);
> @@ -217,13 +218,13 @@ int __irq_set_affinity_locked(struct irq
> return ret;
> }
>
> -/**
> - * irq_set_affinity - Set the irq affinity of a given irq
> - * @irq: Interrupt to set affinity
> - * @mask: cpumask
> - *
> - */
> -int irq_set_affinity(unsigned int irq, const struct cpumask *mask)
> +int __irq_set_affinity_locked(struct irq_data *data,const struct cpumask *mask)
> +{
> + return irq_do_set_affinity_locked(data, mask, false);
> +}
> +
> +static int __irq_set_affinity(unsigned int irq, const struct cpumask *mask,
> + bool force)
> {
> struct irq_desc *desc = irq_to_desc(irq);
> unsigned long flags;
> @@ -233,11 +234,33 @@ int irq_set_affinity(unsigned int irq, c
> return -EINVAL;
>
> raw_spin_lock_irqsave(&desc->lock, flags);
> - ret = __irq_set_affinity_locked(irq_desc_get_irq_data(desc), mask);
> + ret = irq_do_set_affinity_locked(irq_desc_get_irq_data(desc), mask,
> + force);
> raw_spin_unlock_irqrestore(&desc->lock, flags);
> return ret;
> }
>
> +/**
> + * irq_force_affinity - Force the irq affinity of a given irq
> + * @irq: Interrupt to set affinity
> + * @mask: cpumask
> + */
> +int irq_force_affinity(unsigned int irq, const struct cpumask *mask)
> +{
> + return __irq_set_affinity(irq, mask, true);
> +}
> +
> +/**
> + * irq_set_affinity - Set the irq affinity of a given irq
> + * @irq: Interrupt to set affinity
> + * @mask: cpumask
> + *
> + */
> +int irq_set_affinity(unsigned int irq, const struct cpumask *mask)
> +{
> + return __irq_set_affinity(irq, mask, false);
> +}
> +
> int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
> {
> unsigned long flags;
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