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).

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 | 104 ++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 156 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..80b734b --- /dev/null +++ b/include/trace/events/ipi.h @@ -0,0 +1,104 @@ +#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)) + +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) + __array(char, cpumask, NR_CPUS) + ), + + TP_fast_assign( + __entry->ipinr = ipinr; + cpumask_scnprintf(__entry->cpumask, + ARRAY_SIZE(__entry->cpumask), cpumask); + ), + + TP_printk("ipi=%d, cpumask=0x%s, name=%s", __entry->ipinr, __entry->cpumask, + show_ipi_name(__entry->ipinr)) +); + +#endif /* _TRACE_IPI_H */ + +/* This part must be outside protection */ +#include <trace/define_trace.h>