Hi Grygorii,
On 12/08/2016 05:33 PM, Grygorii Strashko wrote:
> From: "Strashko, Grygorii" <grygorii.strashko@xxxxxx>
>
> The below call chain generates "scheduling while atomic" backtrace and
> causes system crash when Keystone 2 IRQ chip driver is used with RT-kernel:
>
> gic_handle_irq()
> |-__handle_domain_irq()
> |-generic_handle_irq()
> |-keystone_irq_handler()
> |-regmap_read()
> |-regmap_lock_spinlock()
> |-rt_spin_lock()
>
> The reason is that Keystone driver dispatches IRQ using chained IRQ handler
> and accesses I/O memory through syscon->regmap(mmio) which is implemented
> as fast_io regmap and uses regular spinlocks for synchronization, but
> spinlocks transformed to rt_mutexes on RT.
>
> Hence, convert Keystone 2 IRQ driver to use generic irq handler instead of
> chained IRQ handler. This way it will be compatible with RT kernel where it
> will be forced thread IRQ handler while in non-RT kernel it still will be
> executed in HW IRQ context.
>
> Cc: Suman Anna <s-anna@xxxxxx>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
> ---
> Hi,
>
> In general, there is an option to convert this driver to use nested threaded
> irq handlers (this should not affect our current user of these irqs from
> performance point of view), but that will affect on our current remoteproc and
> UIO based drivers (including uio core) which do not expect to use threaded
> irq and use request_irq(). These drivers and UIO core might require to be
> updated to use threaded irqs and (or) request_any_context_irq().
>
> Suman, what do you think?
I like the current patch as is as we do not want the downstream
subsystems/interrupt users of this driver to change their design
semantics to have to use threaded irqs, and cause a cascading effect.
Tested-by: Suman Anna <s-anna@xxxxxx>
regards
Suman
>
> drivers/irqchip/irq-keystone.c | 28 +++++++++++++++++++---------
> 1 file changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/irqchip/irq-keystone.c b/drivers/irqchip/irq-keystone.c
> index 54a5e87..efbcf84 100644
> --- a/drivers/irqchip/irq-keystone.c
> +++ b/drivers/irqchip/irq-keystone.c
> @@ -19,9 +19,9 @@
> #include <linux/bitops.h>
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> +#include <linux/interrupt.h>
> #include <linux/irqdomain.h>
> #include <linux/irqchip.h>
> -#include <linux/irqchip/chained_irq.h>
> #include <linux/of.h>
> #include <linux/of_platform.h>
> #include <linux/mfd/syscon.h>
> @@ -39,6 +39,7 @@ struct keystone_irq_device {
> struct irq_domain *irqd;
> struct regmap *devctrl_regs;
> u32 devctrl_offset;
> + raw_spinlock_t wa_lock;
> };
>
> static inline u32 keystone_irq_readl(struct keystone_irq_device *kirq)
> @@ -83,17 +84,15 @@ static void keystone_irq_ack(struct irq_data *d)
> /* nothing to do here */
> }
>
> -static void keystone_irq_handler(struct irq_desc *desc)
> +static irqreturn_t keystone_irq_handler(int irq, void *keystone_irq)
> {
> - unsigned int irq = irq_desc_get_irq(desc);
> - struct keystone_irq_device *kirq = irq_desc_get_handler_data(desc);
> + struct keystone_irq_device *kirq = keystone_irq;
> + unsigned long wa_lock_flags;
> unsigned long pending;
> int src, virq;
>
> dev_dbg(kirq->dev, "start irq %d\n", irq);
>
> - chained_irq_enter(irq_desc_get_chip(desc), desc);
> -
> pending = keystone_irq_readl(kirq);
> keystone_irq_writel(kirq, pending);
>
> @@ -111,13 +110,15 @@ static void keystone_irq_handler(struct irq_desc *desc)
> if (!virq)
> dev_warn(kirq->dev, "spurious irq detected hwirq %d, virq %d\n",
> src, virq);
> + raw_spin_lock_irqsave(&kirq->wa_lock, wa_lock_flags);
> generic_handle_irq(virq);
> + raw_spin_unlock_irqrestore(&kirq->wa_lock,
> + wa_lock_flags);
> }
> }
>
> - chained_irq_exit(irq_desc_get_chip(desc), desc);
> -
> dev_dbg(kirq->dev, "end irq %d\n", irq);
> + return IRQ_HANDLED;
> }
>
> static int keystone_irq_map(struct irq_domain *h, unsigned int virq,
> @@ -182,9 +183,16 @@ static int keystone_irq_probe(struct platform_device *pdev)
> return -ENODEV;
> }
>
> + raw_spin_lock_init(&kirq->wa_lock);
> +
> platform_set_drvdata(pdev, kirq);
>
> - irq_set_chained_handler_and_data(kirq->irq, keystone_irq_handler, kirq);
> + ret = request_irq(kirq->irq, keystone_irq_handler,
> + 0, dev_name(dev), kirq);
> + if (ret) {
> + irq_domain_remove(kirq->irqd);
> + return ret;
> + }
>
> /* clear all source bits */
> keystone_irq_writel(kirq, ~0x0);
> @@ -199,6 +207,8 @@ static int keystone_irq_remove(struct platform_device *pdev)
> struct keystone_irq_device *kirq = platform_get_drvdata(pdev);
> int hwirq;
>
> + free_irq(kirq->irq, kirq);
> +
> for (hwirq = 0; hwirq < KEYSTONE_N_IRQ; hwirq++)
> irq_dispose_mapping(irq_find_mapping(kirq->irqd, hwirq));
>
>
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