| Message ID | 20210924132837.45994-4-kernelfans@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/irqentry: remove duplicate housekeeping of | expand |
On Fri, Sep 24, 2021 at 09:28:35PM +0800, Pingfan Liu wrote: > handle_domain_irq() contains two major parts: > -1. irq_enter()/irq_exit(), which serves as hooks for rcu and trace etc. > -2. irq mapping and dispatching > > After the introduction of irqentry_enter()/irqentry_exit() and arch > specific counterpart (e.g. arm64), roughly speaking, rcu_irq_enter() has > already been called. Hence here comes requirement to move > irq_enter/irq_exit out of handle_domain_irq(). And arches should handle > about irq_enter_rcu()/irq_exit_rcu() by themself. > > Since there is still arches, which does not adopt irqentry_enter(), let > irq_enter()/irq_exit() arch optional in handle_domain_irq(). The patch below looks good to me, but the commit message is a little hard to follow. How about: 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. With that commit message: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Mark. > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > 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: Yuichi Ito <ito-yuichi@fujitsu.com> > Cc: linux-arm-kernel@lists.infradead.org > To: linux-kernel@vger.kernel.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 > > /* 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; > } > -- > 2.31.1 >
On Tue, Sep 28, 2021 at 09:55:00AM +0100, Mark Rutland wrote: > On Fri, Sep 24, 2021 at 09:28:35PM +0800, Pingfan Liu wrote: > > handle_domain_irq() contains two major parts: > > -1. irq_enter()/irq_exit(), which serves as hooks for rcu and trace etc. > > -2. irq mapping and dispatching > > > > After the introduction of irqentry_enter()/irqentry_exit() and arch > > specific counterpart (e.g. arm64), roughly speaking, rcu_irq_enter() has > > already been called. Hence here comes requirement to move > > irq_enter/irq_exit out of handle_domain_irq(). And arches should handle > > about irq_enter_rcu()/irq_exit_rcu() by themself. > > > > Since there is still arches, which does not adopt irqentry_enter(), let > > irq_enter()/irq_exit() arch optional in handle_domain_irq(). > > The patch below looks good to me, but the commit message is a little > hard to follow. How about: > > 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. > Thanks for your precious time to improve the log. It looks great, and I will use it in V2. I will keep learning to improve my level of log. > With that commit message: > > Reviewed-by: Mark Rutland <mark.rutland@arm.com> > Thanks, Pingfan
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 /* 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; }
handle_domain_irq() contains two major parts: -1. irq_enter()/irq_exit(), which serves as hooks for rcu and trace etc. -2. irq mapping and dispatching After the introduction of irqentry_enter()/irqentry_exit() and arch specific counterpart (e.g. arm64), roughly speaking, rcu_irq_enter() has already been called. Hence here comes requirement to move irq_enter/irq_exit out of handle_domain_irq(). And arches should handle about irq_enter_rcu()/irq_exit_rcu() by themself. Since there is still arches, which does not adopt irqentry_enter(), let irq_enter()/irq_exit() arch optional in handle_domain_irq(). Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> 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: Yuichi Ito <ito-yuichi@fujitsu.com> Cc: linux-arm-kernel@lists.infradead.org To: linux-kernel@vger.kernel.org --- kernel/irq/Kconfig | 3 +++ kernel/irq/irqdesc.c | 4 ++++ 2 files changed, 7 insertions(+)