Re: [PATCH] MIPS: SMP: Don't increment irq_count multiple times for call function IPIs

[Alex Smith <alex.smith@imgtec.com>]

On 24/07/2015 16:49, Paul Burton wrote:
> On Fri, Jul 24, 2015 at 04:14:22PM +0100, Alex Smith wrote:
>> The majority of SMP platforms handle their IPIs through do_IRQ()
>> which calls irq_{enter/exit}(). When a call function IPI is received,
>> smp_call_function_interrupt() is called which also calls
>> irq_{enter,exit}(), meaning irq_count is raised twice.
>>
>> When tick broadcasting is used (which is implemented via a call
>> function IPI), this incorrectly causes all CPU idle time on the core
>> receiving broadcast ticks to be accounted as time spent servicing
>> IRQs, as account_process_tick() will account as such if irq_count is
>> greater than 1. This results in 100% CPU usage being reported on a
>> core which receives its ticks via broadcast.
>>
>> This patch removes the SMP smp_call_function_interrupt() wrapper which
>> calls irq_{enter,exit}(). Platforms which handle their IPIs through
>> do_IRQ() now call generic_smp_call_function_interrupt() directly to
>> avoid incrementing irq_count a second time. Platforms which don't
>> (loongson, sgi-ip27, sibyte) call generic_smp_call_function_interrupt()
>> wrapped in irq_{enter,exit}().
>>
>> Signed-off-by: Alex Smith <alex.smith@imgtec.com>
>> ---
>>   arch/mips/cavium-octeon/smp.c         |  2 +-
>>   arch/mips/include/asm/smp.h           |  2 --
>>   arch/mips/kernel/smp-bmips.c          |  4 ++--
>>   arch/mips/kernel/smp.c                | 10 ----------
>>   arch/mips/lantiq/irq.c                |  2 +-
>>   arch/mips/loongson64/loongson-3/smp.c |  7 +++++--
>>   arch/mips/mti-malta/malta-int.c       |  2 +-
>>   arch/mips/netlogic/common/smp.c       |  2 +-
>>   arch/mips/paravirt/paravirt-smp.c     |  2 +-
>>   arch/mips/pmcs-msp71xx/msp_smp.c      |  2 +-
>>   arch/mips/sgi-ip27/ip27-irq.c         |  8 ++++++--
>>   arch/mips/sibyte/bcm1480/smp.c        |  9 +++++----
>>   arch/mips/sibyte/sb1250/smp.c         |  7 +++++--
>>   13 files changed, 29 insertions(+), 30 deletions(-)
>
> Hi Alex,
>
> I think you'll need to catch the case in drivers/irqchip/irq-mips-gic.c
> too.
>
> Thanks,
>      Paul

You're right, I do, thanks.

I'll send v2.

Alex

>
>> diff --git a/arch/mips/cavium-octeon/smp.c b/arch/mips/cavium-octeon/smp.c
>> index 56f5d080ef9d..b7fa9ae28c36 100644
>> --- a/arch/mips/cavium-octeon/smp.c
>> +++ b/arch/mips/cavium-octeon/smp.c
>> @@ -42,7 +42,7 @@ static irqreturn_t mailbox_interrupt(int irq, void *dev_id)
>>   	cvmx_write_csr(CVMX_CIU_MBOX_CLRX(coreid), action);
>>
>>   	if (action & SMP_CALL_FUNCTION)
>> -		smp_call_function_interrupt();
>> +		generic_smp_call_function_interrupt();
>>   	if (action & SMP_RESCHEDULE_YOURSELF)
>>   		scheduler_ipi();
>>
>> diff --git a/arch/mips/include/asm/smp.h b/arch/mips/include/asm/smp.h
>> index 16f1ea9ab191..03722d4326a1 100644
>> --- a/arch/mips/include/asm/smp.h
>> +++ b/arch/mips/include/asm/smp.h
>> @@ -83,8 +83,6 @@ static inline void __cpu_die(unsigned int cpu)
>>   extern void play_dead(void);
>>   #endif
>>
>> -extern asmlinkage void smp_call_function_interrupt(void);
>> -
>>   static inline void arch_send_call_function_single_ipi(int cpu)
>>   {
>>   	extern struct plat_smp_ops *mp_ops;	/* private */
>> diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c
>> index 336708ae5c5b..78cf8c2f1de0 100644
>> --- a/arch/mips/kernel/smp-bmips.c
>> +++ b/arch/mips/kernel/smp-bmips.c
>> @@ -284,7 +284,7 @@ static irqreturn_t bmips5000_ipi_interrupt(int irq, void *dev_id)
>>   	if (action == 0)
>>   		scheduler_ipi();
>>   	else
>> -		smp_call_function_interrupt();
>> +		generic_smp_call_function_interrupt();
>>
>>   	return IRQ_HANDLED;
>>   }
>> @@ -336,7 +336,7 @@ static irqreturn_t bmips43xx_ipi_interrupt(int irq, void *dev_id)
>>   	if (action & SMP_RESCHEDULE_YOURSELF)
>>   		scheduler_ipi();
>>   	if (action & SMP_CALL_FUNCTION)
>> -		smp_call_function_interrupt();
>> +		generic_smp_call_function_interrupt();
>>
>>   	return IRQ_HANDLED;
>>   }
>> diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
>> index d0744cc77ea7..a31896c33716 100644
>> --- a/arch/mips/kernel/smp.c
>> +++ b/arch/mips/kernel/smp.c
>> @@ -192,16 +192,6 @@ asmlinkage void start_secondary(void)
>>   	cpu_startup_entry(CPUHP_ONLINE);
>>   }
>>
>> -/*
>> - * Call into both interrupt handlers, as we share the IPI for them
>> - */
>> -void __irq_entry smp_call_function_interrupt(void)
>> -{
>> -	irq_enter();
>> -	generic_smp_call_function_interrupt();
>> -	irq_exit();
>> -}
>> -
>>   static void stop_this_cpu(void *dummy)
>>   {
>>   	/*
>> diff --git a/arch/mips/lantiq/irq.c b/arch/mips/lantiq/irq.c
>> index 6ab10573490d..be18648cb8c8 100644
>> --- a/arch/mips/lantiq/irq.c
>> +++ b/arch/mips/lantiq/irq.c
>> @@ -293,7 +293,7 @@ static irqreturn_t ipi_resched_interrupt(int irq, void *dev_id)
>>
>>   static irqreturn_t ipi_call_interrupt(int irq, void *dev_id)
>>   {
>> -	smp_call_function_interrupt();
>> +	generic_smp_call_function_interrupt();
>>   	return IRQ_HANDLED;
>>   }
>>
>> diff --git a/arch/mips/loongson64/loongson-3/smp.c b/arch/mips/loongson64/loongson-3/smp.c
>> index 509877c6e9d9..1a4738a8f2d3 100644
>> --- a/arch/mips/loongson64/loongson-3/smp.c
>> +++ b/arch/mips/loongson64/loongson-3/smp.c
>> @@ -266,8 +266,11 @@ void loongson3_ipi_interrupt(struct pt_regs *regs)
>>   	if (action & SMP_RESCHEDULE_YOURSELF)
>>   		scheduler_ipi();
>>
>> -	if (action & SMP_CALL_FUNCTION)
>> -		smp_call_function_interrupt();
>> +	if (action & SMP_CALL_FUNCTION) {
>> +		irq_enter();
>> +		generic_smp_call_function_interrupt();
>> +		irq_exit();
>> +	}
>>
>>   	if (action & SMP_ASK_C0COUNT) {
>>   		BUG_ON(cpu != 0);
>> diff --git a/arch/mips/mti-malta/malta-int.c b/arch/mips/mti-malta/malta-int.c
>> index d1392f8f5811..fa8f591f3713 100644
>> --- a/arch/mips/mti-malta/malta-int.c
>> +++ b/arch/mips/mti-malta/malta-int.c
>> @@ -222,7 +222,7 @@ static irqreturn_t ipi_resched_interrupt(int irq, void *dev_id)
>>
>>   static irqreturn_t ipi_call_interrupt(int irq, void *dev_id)
>>   {
>> -	smp_call_function_interrupt();
>> +	generic_smp_call_function_interrupt();
>>
>>   	return IRQ_HANDLED;
>>   }
>> diff --git a/arch/mips/netlogic/common/smp.c b/arch/mips/netlogic/common/smp.c
>> index dc3e327fbbac..f5fff228b347 100644
>> --- a/arch/mips/netlogic/common/smp.c
>> +++ b/arch/mips/netlogic/common/smp.c
>> @@ -86,7 +86,7 @@ void nlm_smp_function_ipi_handler(unsigned int irq, struct irq_desc *desc)
>>   {
>>   	clear_c0_eimr(irq);
>>   	ack_c0_eirr(irq);
>> -	smp_call_function_interrupt();
>> +	generic_smp_call_function_interrupt();
>>   	set_c0_eimr(irq);
>>   }
>>
>> diff --git a/arch/mips/paravirt/paravirt-smp.c b/arch/mips/paravirt/paravirt-smp.c
>> index 42181c7105df..f8d3e081b2eb 100644
>> --- a/arch/mips/paravirt/paravirt-smp.c
>> +++ b/arch/mips/paravirt/paravirt-smp.c
>> @@ -114,7 +114,7 @@ static irqreturn_t paravirt_reched_interrupt(int irq, void *dev_id)
>>
>>   static irqreturn_t paravirt_function_interrupt(int irq, void *dev_id)
>>   {
>> -	smp_call_function_interrupt();
>> +	generic_smp_call_function_interrupt();
>>   	return IRQ_HANDLED;
>>   }
>>
>> diff --git a/arch/mips/pmcs-msp71xx/msp_smp.c b/arch/mips/pmcs-msp71xx/msp_smp.c
>> index 10170580a2de..ffa0f7101a97 100644
>> --- a/arch/mips/pmcs-msp71xx/msp_smp.c
>> +++ b/arch/mips/pmcs-msp71xx/msp_smp.c
>> @@ -44,7 +44,7 @@ static irqreturn_t ipi_resched_interrupt(int irq, void *dev_id)
>>
>>   static irqreturn_t ipi_call_interrupt(int irq, void *dev_id)
>>   {
>> -	smp_call_function_interrupt();
>> +	generic_smp_call_function_interrupt();
>>
>>   	return IRQ_HANDLED;
>>   }
>> diff --git a/arch/mips/sgi-ip27/ip27-irq.c b/arch/mips/sgi-ip27/ip27-irq.c
>> index 3fbaef97a1b8..16ec4e12daa3 100644
>> --- a/arch/mips/sgi-ip27/ip27-irq.c
>> +++ b/arch/mips/sgi-ip27/ip27-irq.c
>> @@ -107,10 +107,14 @@ static void ip27_do_irq_mask0(void)
>>   		scheduler_ipi();
>>   	} else if (pend0 & (1UL << CPU_CALL_A_IRQ)) {
>>   		LOCAL_HUB_CLR_INTR(CPU_CALL_A_IRQ);
>> -		smp_call_function_interrupt();
>> +		irq_enter();
>> +		generic_smp_call_function_interrupt();
>> +		irq_exit();
>>   	} else if (pend0 & (1UL << CPU_CALL_B_IRQ)) {
>>   		LOCAL_HUB_CLR_INTR(CPU_CALL_B_IRQ);
>> -		smp_call_function_interrupt();
>> +		irq_enter();
>> +		generic_smp_call_function_interrupt();
>> +		irq_exit();
>>   	} else
>>   #endif
>>   	{
>> diff --git a/arch/mips/sibyte/bcm1480/smp.c b/arch/mips/sibyte/bcm1480/smp.c
>> index af7d44edd9a8..4c71aea25663 100644
>> --- a/arch/mips/sibyte/bcm1480/smp.c
>> +++ b/arch/mips/sibyte/bcm1480/smp.c
>> @@ -29,8 +29,6 @@
>>   #include <asm/sibyte/bcm1480_regs.h>
>>   #include <asm/sibyte/bcm1480_int.h>
>>
>> -extern void smp_call_function_interrupt(void);
>> -
>>   /*
>>    * These are routines for dealing with the bcm1480 smp capabilities
>>    * independent of board/firmware
>> @@ -184,6 +182,9 @@ void bcm1480_mailbox_interrupt(void)
>>   	if (action & SMP_RESCHEDULE_YOURSELF)
>>   		scheduler_ipi();
>>
>> -	if (action & SMP_CALL_FUNCTION)
>> -		smp_call_function_interrupt();
>> +	if (action & SMP_CALL_FUNCTION) {
>> +		irq_enter();
>> +		generic_smp_call_function_interrupt();
>> +		irq_exit();
>> +	}
>>   }
>> diff --git a/arch/mips/sibyte/sb1250/smp.c b/arch/mips/sibyte/sb1250/smp.c
>> index c0c4b3f88a08..1cf66f5ff23d 100644
>> --- a/arch/mips/sibyte/sb1250/smp.c
>> +++ b/arch/mips/sibyte/sb1250/smp.c
>> @@ -172,6 +172,9 @@ void sb1250_mailbox_interrupt(void)
>>   	if (action & SMP_RESCHEDULE_YOURSELF)
>>   		scheduler_ipi();
>>
>> -	if (action & SMP_CALL_FUNCTION)
>> -		smp_call_function_interrupt();
>> +	if (action & SMP_CALL_FUNCTION) {
>> +		irq_enter();
>> +		generic_smp_call_function_interrupt();
>> +		irq_exit();
>> +	}
>>   }
>> --
>> 2.4.6
>>
>>