[V3] ARM: trace: Add tracepoint for the Inter Processor Interrupt

The Inter Processor Interrupt is used on ARM to tell another processor to do
a specific action. This is mainly used to emulate a timer interrupt on an idle
cpu, force a cpu to reschedule or run a function on another processor context.

Add a tracepoint when raising an IPI and in the entry/exit handler functions.

When a cpu raises an IPI, the targeted cpus is an interesting information, the
cpumask conversion in hexa is added in the trace using the cpumask_scnprintf
function.

Tested-on Vexpress TC2 (5 processors).
Tested-on u8500 (2 processors).

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 arch/arm/include/asm/smp.h   |    9 ++++
 arch/arm/kernel/smp.c        |   34 +++++++------
 arch/arm64/include/asm/smp.h |    7 +++
 arch/arm64/kernel/smp.c      |   21 ++++++--
 include/trace/events/ipi.h   |  112 ++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 164 insertions(+), 19 deletions(-)
 create mode 100644 include/trace/events/ipi.h

On 11/07/2013 10:01 AM, Daniel Lezcano wrote:
> The Inter Processor Interrupt is used on ARM to tell another processor to do
> a specific action. This is mainly used to emulate a timer interrupt on an idle
> cpu, force a cpu to reschedule or run a function on another processor context.
>
> Add a tracepoint when raising an IPI and in the entry/exit handler functions.
>
> When a cpu raises an IPI, the targeted cpus is an interesting information, the
> cpumask conversion in hexa is added in the trace using the cpumask_scnprintf
> function.
>
> Tested-on Vexpress TC2 (5 processors).
> Tested-on u8500 (2 processors).
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

Hi guys,

did you have time to look at this patch ?

We are writing a tool [1] to do some statistics about the cpu's idle 
times and giving the source of the wakeup. We hope it could be useful 
for the community to do some measurements but we need the IPI 
tracepoints to be more accurate.

Thanks in advance
   -- Daniel

[1] https://git.linaro.org/gitweb?p=tools/idlestat.git;a=summary

> ---
>   arch/arm/include/asm/smp.h   |    9 ++++
>   arch/arm/kernel/smp.c        |   34 +++++++------
>   arch/arm64/include/asm/smp.h |    7 +++
>   arch/arm64/kernel/smp.c      |   21 ++++++--
>   include/trace/events/ipi.h   |  112 ++++++++++++++++++++++++++++++++++++++++++
>   5 files changed, 164 insertions(+), 19 deletions(-)
>   create mode 100644 include/trace/events/ipi.h
>
> diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h
> index a8cae71c..788706c 100644
> --- a/arch/arm/include/asm/smp.h
> +++ b/arch/arm/include/asm/smp.h
> @@ -18,6 +18,15 @@
>   # error "<asm/smp.h> included in non-SMP build"
>   #endif
>
> +enum ipi_msg_type {
> +	IPI_WAKEUP,
> +	IPI_TIMER,
> +	IPI_RESCHEDULE,
> +	IPI_CALL_FUNC,
> +	IPI_CALL_FUNC_SINGLE,
> +	IPI_CPU_STOP,
> +};
> +
>   #define raw_smp_processor_id() (current_thread_info()->cpu)
>
>   struct seq_file;
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 72024ea..9ca8ce8 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -46,6 +46,9 @@
>   #include <asm/mach/arch.h>
>   #include <asm/mpu.h>
>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/ipi.h>
> +
>   /*
>    * as from 2.5, kernels no longer have an init_tasks structure
>    * so we need some other way of telling a new secondary core
> @@ -59,15 +62,6 @@ struct secondary_data secondary_data;
>    */
>   volatile int pen_release = -1;
>
> -enum ipi_msg_type {
> -	IPI_WAKEUP,
> -	IPI_TIMER,
> -	IPI_RESCHEDULE,
> -	IPI_CALL_FUNC,
> -	IPI_CALL_FUNC_SINGLE,
> -	IPI_CPU_STOP,
> -};
> -
>   static DECLARE_COMPLETION(cpu_running);
>
>   static struct smp_operations smp_ops;
> @@ -433,19 +427,25 @@ void __init set_smp_cross_call(void (*fn)(const struct cpumask *, unsigned int))
>   		smp_cross_call = fn;
>   }
>
> +static void ipi_raise(const struct cpumask *mask, int ipinr)
> +{
> +	trace_ipi_raise(mask, ipinr);
> +	smp_cross_call(mask, ipinr);
> +}
> +
>   void arch_send_call_function_ipi_mask(const struct cpumask *mask)
>   {
> -	smp_cross_call(mask, IPI_CALL_FUNC);
> +	ipi_raise(mask, IPI_CALL_FUNC);
>   }
>
>   void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
>   {
> -	smp_cross_call(mask, IPI_WAKEUP);
> +	ipi_raise(mask, IPI_WAKEUP);
>   }
>
>   void arch_send_call_function_single_ipi(int cpu)
>   {
> -	smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
> +	ipi_raise(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
>   }
>
>   static const char *ipi_types[NR_IPI] = {
> @@ -487,7 +487,7 @@ u64 smp_irq_stat_cpu(unsigned int cpu)
>   #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
>   void tick_broadcast(const struct cpumask *mask)
>   {
> -	smp_cross_call(mask, IPI_TIMER);
> +	ipi_raise(mask, IPI_TIMER);
>   }
>   #endif
>
> @@ -528,6 +528,8 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
>   	unsigned int cpu = smp_processor_id();
>   	struct pt_regs *old_regs = set_irq_regs(regs);
>
> +	trace_ipi_handler_entry(ipinr);
> +
>   	if (ipinr < NR_IPI)
>   		__inc_irq_stat(cpu, ipi_irqs[ipinr]);
>
> @@ -571,11 +573,13 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
>   		break;
>   	}
>   	set_irq_regs(old_regs);
> +
> +	trace_ipi_handler_exit(ipinr);
>   }
>
>   void smp_send_reschedule(int cpu)
>   {
> -	smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
> +	ipi_raise(cpumask_of(cpu), IPI_RESCHEDULE);
>   }
>
>   void smp_send_stop(void)
> @@ -586,7 +590,7 @@ void smp_send_stop(void)
>   	cpumask_copy(&mask, cpu_online_mask);
>   	cpumask_clear_cpu(smp_processor_id(), &mask);
>   	if (!cpumask_empty(&mask))
> -		smp_cross_call(&mask, IPI_CPU_STOP);
> +		ipi_raise(&mask, IPI_CPU_STOP);
>
>   	/* Wait up to one second for other CPUs to stop */
>   	timeout = USEC_PER_SEC;
> diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
> index 4b8023c..7ebaa3a 100644
> --- a/arch/arm64/include/asm/smp.h
> +++ b/arch/arm64/include/asm/smp.h
> @@ -24,6 +24,13 @@
>   # error "<asm/smp.h> included in non-SMP build"
>   #endif
>
> +enum ipi_msg_type {
> +	IPI_RESCHEDULE,
> +	IPI_CALL_FUNC,
> +	IPI_CALL_FUNC_SINGLE,
> +	IPI_CPU_STOP,
> +};
> +
>   #define raw_smp_processor_id() (current_thread_info()->cpu)
>
>   struct seq_file;
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 78db90d..c987b9f 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -48,6 +48,9 @@
>   #include <asm/tlbflush.h>
>   #include <asm/ptrace.h>
>
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/ipi.h>
> +
>   /*
>    * as from 2.5, kernels no longer have an init_tasks structure
>    * so we need some other way of telling a new secondary core
> @@ -426,14 +429,20 @@ void __init set_smp_cross_call(void (*fn)(const struct cpumask *, unsigned int))
>   	smp_cross_call = fn;
>   }
>
> +static void ipi_raise(const struct cpumask *mask, int ipinr)
> +{
> +	trace_ipi_raise(mask, ipinr);
> +	smp_cross_call(mask, ipinr);
> +}
> +
>   void arch_send_call_function_ipi_mask(const struct cpumask *mask)
>   {
> -	smp_cross_call(mask, IPI_CALL_FUNC);
> +	ipi_raise(mask, IPI_CALL_FUNC);
>   }
>
>   void arch_send_call_function_single_ipi(int cpu)
>   {
> -	smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
> +	ipi_raise(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
>   }
>
>   static const char *ipi_types[NR_IPI] = {
> @@ -501,6 +510,8 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
>   	unsigned int cpu = smp_processor_id();
>   	struct pt_regs *old_regs = set_irq_regs(regs);
>
> +	trace_ipi_handler_entry(ipinr);
> +
>   	if (ipinr >= IPI_RESCHEDULE && ipinr < IPI_RESCHEDULE + NR_IPI)
>   		__inc_irq_stat(cpu, ipi_irqs[ipinr - IPI_RESCHEDULE]);
>
> @@ -532,11 +543,13 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
>   		break;
>   	}
>   	set_irq_regs(old_regs);
> +
> +	trace_ipi_handler_exit(ipinr);
>   }
>
>   void smp_send_reschedule(int cpu)
>   {
> -	smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
> +	ipi_raise(cpumask_of(cpu), IPI_RESCHEDULE);
>   }
>
>   void smp_send_stop(void)
> @@ -549,7 +562,7 @@ void smp_send_stop(void)
>   		cpumask_copy(&mask, cpu_online_mask);
>   		cpu_clear(smp_processor_id(), mask);
>
> -		smp_cross_call(&mask, IPI_CPU_STOP);
> +		ipi_raise(&mask, IPI_CPU_STOP);
>   	}
>
>   	/* Wait up to one second for other CPUs to stop */
> diff --git a/include/trace/events/ipi.h b/include/trace/events/ipi.h
> new file mode 100644
> index 0000000..fa22d4f
> --- /dev/null
> +++ b/include/trace/events/ipi.h
> @@ -0,0 +1,112 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM ipi
> +
> +#if !defined(_TRACE_IPI_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_IPI_H
> +
> +#include <linux/tracepoint.h>
> +
> +#define ipi_name(ipinr) { IPI_##ipinr, #ipinr }
> +#define show_ipi_name(val)				\
> +	__print_symbolic(val,				\
> +			 ipi_name(WAKEUP),		\
> +			 ipi_name(TIMER),		\
> +			 ipi_name(RESCHEDULE),		\
> +			 ipi_name(CALL_FUNC),		\
> +			 ipi_name(CALL_FUNC_SINGLE),	\
> +			 ipi_name(CPU_STOP))
> +
> +#define show_cpumask(srcp)				\
> +	({						\
> +		char *buf = __get_dynamic_array(buf);	\
> +		cpumask_scnprintf(buf, NR_CPUS, srcp);	\
> +		buf;					\
> +	})
> +
> +DECLARE_EVENT_CLASS(ipi,
> +
> +    TP_PROTO(int ipinr),
> +
> +    TP_ARGS(ipinr),
> +
> +    TP_STRUCT__entry(
> +	    __field(int, ipinr)
> +    ),
> +
> +    TP_fast_assign(
> +	    __entry->ipinr = ipinr;
> +    ),
> +
> +    TP_printk("ipi=%d, name=%s", __entry->ipinr,
> +	      show_ipi_name(__entry->ipinr))
> +);
> +
> +/**
> + * ipi_handle_entry - called right before the IPI handler
> + * @ipinr: the IPI number
> + *
> + * The @ipinr value must be valid and the action name associated with
> + * the IPI value is given in the trace.
> + */
> +DEFINE_EVENT_CONDITION(ipi, ipi_handler_entry,
> +
> +    TP_PROTO(int ipinr),
> +
> +    TP_ARGS(ipinr),
> +
> +    TP_CONDITION(ipinr < NR_IPI && ipinr >= 0)
> +);
> +
> +/**
> + * ipi_handle_exit - called right after the IPI handler
> + * @ipinr: the IPI number
> + *
> + * The @ipinr value must be valid and the action name associated with
> + * the IPI value is given in the trace.
> + */
> +DEFINE_EVENT_CONDITION(ipi, ipi_handler_exit,
> +
> +    TP_PROTO(int ipinr),
> +
> +    TP_ARGS(ipinr),
> +
> +    TP_CONDITION(ipinr < NR_IPI && ipinr >= 0)
> +);
> +
> +/**
> + * ipi_raise - called when a smp cross call is made
> + * @ipinr: the IPI number
> + * @cpumask: the recipients for the IPI
> + *
> + * The @ipinr value must be valid and the action name associated with
> + * the IPI value is given in the trace as well as the cpumask of the
> + * targeted cpus.
> + */
> +TRACE_EVENT_CONDITION(ipi_raise,
> +
> +    TP_PROTO(const struct cpumask *cpumask, int ipinr),
> +
> +    TP_ARGS(cpumask, ipinr),
> +
> +    TP_CONDITION(ipinr < NR_IPI && ipinr >= 0),
> +
> +    TP_STRUCT__entry(
> +	    __field(int, ipinr)
> +	    __field(const struct cpumask *, cpumask)
> +	    __dynamic_array(char, buf, NR_CPUS)
> +    ),
> +
> +    TP_fast_assign(
> +	    __entry->ipinr = ipinr;
> +	    __entry->cpumask = cpumask;
> +    ),
> +
> +    TP_printk("ipi=%d, cpumask=0x%s, name=%s", __entry->ipinr,
> +	      show_cpumask(__entry->cpumask),
> +	      show_ipi_name(__entry->ipinr))
> +);
> +
> +#endif /* _TRACE_IPI_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
>