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SubjectRe: [PATCHv3 1/3] kernel/irq: make irq_{enter,exit}() in handle_domain_irq() arch optional
On Thu, 30 Sep 2021 14:17:06 +0100,
Pingfan Liu <kernelfans@gmail.com> wrote:
>
> When an IRQ is taken, some accounting needs to be performed to enter and
> exit IRQ context around the IRQ handler. Historically arch code would
> leave this to the irqchip or core IRQ code, but these days we want this
> to happen in exception entry code, and architectures such as arm64 do
> this.
>
> Currently handle_domain_irq() performs this entry/exit accounting, and
> if used on an architecture where the entry code also does this, the
> entry/exit accounting will be performed twice per IRQ. This is
> problematic as core RCU code such as rcu_is_cpu_rrupt_from_idle()
> depends on this happening once per IRQ, and will not detect quescent
> periods correctly, leading to stall warnings.
>
> As irqchip drivers which use handle_domain_irq() need to work on
> architectures with or without their own entry/exit accounting, this
> patch makes handle_domain_irq() conditionally perform the entry
> accounting depending on a new HAVE_ARCH_IRQENTRY Kconfig symbol that
> architectures can select if they perform this entry accounting
> themselves.
>
> For architectures which do not select the symbol. there should be no
> functional change as a result of this patch.
>
> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> Reviewed-by: Mark Rutland <mark.rutland@arm.com>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Joey Gouly <joey.gouly@arm.com>
> Cc: Sami Tolvanen <samitolvanen@google.com>
> Cc: Julien Thierry <julien.thierry@arm.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Yuichi Ito <ito-yuichi@fujitsu.com>
> Cc: linux-kernel@vger.kernel.org
> To: linux-arm-kernel@lists.infradead.org
> ---
> kernel/irq/Kconfig | 3 +++
> kernel/irq/irqdesc.c | 4 ++++
> 2 files changed, 7 insertions(+)
>
> diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
> index fbc54c2a7f23..defa1db2d664 100644
> --- a/kernel/irq/Kconfig
> +++ b/kernel/irq/Kconfig
> @@ -100,6 +100,9 @@ config IRQ_MSI_IOMMU
> config HANDLE_DOMAIN_IRQ
> bool
>
> +config HAVE_ARCH_IRQENTRY
> + bool
> +
> config IRQ_TIMINGS
> bool
>
> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index 4e3c29bb603c..fd5dd9d278b5 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -693,7 +693,9 @@ int handle_domain_irq(struct irq_domain *domain,
> struct irq_desc *desc;
> int ret = 0;
>
> +#ifndef CONFIG_HAVE_ARCH_IRQENTRY
> irq_enter();
> +#endif

nit: I tend to prefer the 'if (!IS_ENABLED(CONFIG_*))' approach.

>
> /* The irqdomain code provides boundary checks */
> desc = irq_resolve_mapping(domain, hwirq);
> @@ -702,7 +704,9 @@ int handle_domain_irq(struct irq_domain *domain,
> else
> ret = -EINVAL;
>
> +#ifndef CONFIG_HAVE_ARCH_IRQENTRY
> irq_exit();
> +#endif
> set_irq_regs(old_regs);
> return ret;
> }

Apart from that:

Reviewed-by: Marc Zyngier <maz@kernel.org>

Thanks,

M.

--
Without deviation from the norm, progress is not possible.
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