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android-kvm / linux / 85eee6341abb81ac6a35062ffd5c3029eb53be6b / . / kernel / trace / trace_osnoise.c
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// SPDX-License-Identifier: GPL-2.0
/*
* OS Noise Tracer: computes the OS Noise suffered by a running thread.
* Timerlat Tracer: measures the wakeup latency of a timer triggered IRQ and thread.
*
* Based on "hwlat_detector" tracer by:
* Copyright (C) 2008-2009 Jon Masters, Red Hat, Inc. <jcm@redhat.com>
* Copyright (C) 2013-2016 Steven Rostedt, Red Hat, Inc. <srostedt@redhat.com>
* With feedback from Clark Williams <williams@redhat.com>
*
* And also based on the rtsl tracer presented on:
* DE OLIVEIRA, Daniel Bristot, et al. Demystifying the real-time linux
* scheduling latency. In: 32nd Euromicro Conference on Real-Time Systems
* (ECRTS 2020). Schloss Dagstuhl-Leibniz-Zentrum fur Informatik, 2020.
*
* Copyright (C) 2021 Daniel Bristot de Oliveira, Red Hat, Inc. <bristot@redhat.com>
*/
#include <linux/kthread.h>
#include <linux/tracefs.h>
#include <linux/uaccess.h>
#include <linux/cpumask.h>
#include <linux/delay.h>
#include <linux/sched/clock.h>
#include <uapi/linux/sched/types.h>
#include <linux/sched.h>
#include "trace.h"
#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/trace/irq_vectors.h>
#undef TRACE_INCLUDE_PATH
#undef TRACE_INCLUDE_FILE
#endif /* CONFIG_X86_LOCAL_APIC */
#include <trace/events/irq.h>
#include <trace/events/sched.h>
#define CREATE_TRACE_POINTS
#include <trace/events/osnoise.h>
/*
* Default values.
*/
#define BANNER "osnoise: "
#define DEFAULT_SAMPLE_PERIOD 1000000 /* 1s */
#define DEFAULT_SAMPLE_RUNTIME 1000000 /* 1s */
#define DEFAULT_TIMERLAT_PERIOD 1000 /* 1ms */
#define DEFAULT_TIMERLAT_PRIO 95 /* FIFO 95 */
/*
* trace_array of the enabled osnoise/timerlat instances.
*/
struct osnoise_instance {
struct list_head list;
struct trace_array *tr;
};
static struct list_head osnoise_instances;
static bool osnoise_has_registered_instances(void)
{
return !!list_first_or_null_rcu(&osnoise_instances,
struct osnoise_instance,
list);
}
/*
* osnoise_instance_registered - check if a tr is already registered
*/
static int osnoise_instance_registered(struct trace_array *tr)
{
struct osnoise_instance *inst;
int found = 0;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
if (inst->tr == tr)
found = 1;
}
rcu_read_unlock();
return found;
}
/*
* osnoise_register_instance - register a new trace instance
*
* Register a trace_array *tr in the list of instances running
* osnoise/timerlat tracers.
*/
static int osnoise_register_instance(struct trace_array *tr)
{
struct osnoise_instance *inst;
/*
* register/unregister serialization is provided by trace's
* trace_types_lock.
*/
lockdep_assert_held(&trace_types_lock);
inst = kmalloc(sizeof(*inst), GFP_KERNEL);
if (!inst)
return -ENOMEM;
INIT_LIST_HEAD_RCU(&inst->list);
inst->tr = tr;
list_add_tail_rcu(&inst->list, &osnoise_instances);
return 0;
}
/*
* osnoise_unregister_instance - unregister a registered trace instance
*
* Remove the trace_array *tr from the list of instances running
* osnoise/timerlat tracers.
*/
static void osnoise_unregister_instance(struct trace_array *tr)
{
struct osnoise_instance *inst;
int found = 0;
/*
* register/unregister serialization is provided by trace's
* trace_types_lock.
*/
lockdep_assert_held(&trace_types_lock);
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
if (inst->tr == tr) {
list_del_rcu(&inst->list);
found = 1;
break;
}
}
if (!found)
return;
kvfree_rcu(inst);
}
/*
* NMI runtime info.
*/
struct osn_nmi {
u64 count;
u64 delta_start;
};
/*
* IRQ runtime info.
*/
struct osn_irq {
u64 count;
u64 arrival_time;
u64 delta_start;
};
#define IRQ_CONTEXT 0
#define THREAD_CONTEXT 1
/*
* sofirq runtime info.
*/
struct osn_softirq {
u64 count;
u64 arrival_time;
u64 delta_start;
};
/*
* thread runtime info.
*/
struct osn_thread {
u64 count;
u64 arrival_time;
u64 delta_start;
};
/*
* Runtime information: this structure saves the runtime information used by
* one sampling thread.
*/
struct osnoise_variables {
struct task_struct *kthread;
bool sampling;
pid_t pid;
struct osn_nmi nmi;
struct osn_irq irq;
struct osn_softirq softirq;
struct osn_thread thread;
local_t int_counter;
};
/*
* Per-cpu runtime information.
*/
DEFINE_PER_CPU(struct osnoise_variables, per_cpu_osnoise_var);
/*
* this_cpu_osn_var - Return the per-cpu osnoise_variables on its relative CPU
*/
static inline struct osnoise_variables *this_cpu_osn_var(void)
{
return this_cpu_ptr(&per_cpu_osnoise_var);
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* Runtime information for the timer mode.
*/
struct timerlat_variables {
struct task_struct *kthread;
struct hrtimer timer;
u64 rel_period;
u64 abs_period;
bool tracing_thread;
u64 count;
};
DEFINE_PER_CPU(struct timerlat_variables, per_cpu_timerlat_var);
/*
* this_cpu_tmr_var - Return the per-cpu timerlat_variables on its relative CPU
*/
static inline struct timerlat_variables *this_cpu_tmr_var(void)
{
return this_cpu_ptr(&per_cpu_timerlat_var);
}
/*
* tlat_var_reset - Reset the values of the given timerlat_variables
*/
static inline void tlat_var_reset(void)
{
struct timerlat_variables *tlat_var;
int cpu;
/*
* So far, all the values are initialized as 0, so
* zeroing the structure is perfect.
*/
for_each_cpu(cpu, cpu_online_mask) {
tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu);
memset(tlat_var, 0, sizeof(*tlat_var));
}
}
#else /* CONFIG_TIMERLAT_TRACER */
#define tlat_var_reset() do {} while (0)
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* osn_var_reset - Reset the values of the given osnoise_variables
*/
static inline void osn_var_reset(void)
{
struct osnoise_variables *osn_var;
int cpu;
/*
* So far, all the values are initialized as 0, so
* zeroing the structure is perfect.
*/
for_each_cpu(cpu, cpu_online_mask) {
osn_var = per_cpu_ptr(&per_cpu_osnoise_var, cpu);
memset(osn_var, 0, sizeof(*osn_var));
}
}
/*
* osn_var_reset_all - Reset the value of all per-cpu osnoise_variables
*/
static inline void osn_var_reset_all(void)
{
osn_var_reset();
tlat_var_reset();
}
/*
* Tells NMIs to call back to the osnoise tracer to record timestamps.
*/
bool trace_osnoise_callback_enabled;
/*
* osnoise sample structure definition. Used to store the statistics of a
* sample run.
*/
struct osnoise_sample {
u64 runtime; /* runtime */
u64 noise; /* noise */
u64 max_sample; /* max single noise sample */
int hw_count; /* # HW (incl. hypervisor) interference */
int nmi_count; /* # NMIs during this sample */
int irq_count; /* # IRQs during this sample */
int softirq_count; /* # softirqs during this sample */
int thread_count; /* # threads during this sample */
};
#ifdef CONFIG_TIMERLAT_TRACER
/*
* timerlat sample structure definition. Used to store the statistics of
* a sample run.
*/
struct timerlat_sample {
u64 timer_latency; /* timer_latency */
unsigned int seqnum; /* unique sequence */
int context; /* timer context */
};
#endif
/*
* Protect the interface.
*/
struct mutex interface_lock;
/*
* Tracer data.
*/
static struct osnoise_data {
u64 sample_period; /* total sampling period */
u64 sample_runtime; /* active sampling portion of period */
u64 stop_tracing; /* stop trace in the internal operation (loop/irq) */
u64 stop_tracing_total; /* stop trace in the final operation (report/thread) */
#ifdef CONFIG_TIMERLAT_TRACER
u64 timerlat_period; /* timerlat period */
u64 print_stack; /* print IRQ stack if total > */
int timerlat_tracer; /* timerlat tracer */
#endif
bool tainted; /* infor users and developers about a problem */
} osnoise_data = {
.sample_period = DEFAULT_SAMPLE_PERIOD,
.sample_runtime = DEFAULT_SAMPLE_RUNTIME,
.stop_tracing = 0,
.stop_tracing_total = 0,
#ifdef CONFIG_TIMERLAT_TRACER
.print_stack = 0,
.timerlat_period = DEFAULT_TIMERLAT_PERIOD,
.timerlat_tracer = 0,
#endif
};
#ifdef CONFIG_TIMERLAT_TRACER
static inline bool timerlat_enabled(void)
{
return osnoise_data.timerlat_tracer;
}
static inline int timerlat_softirq_exit(struct osnoise_variables *osn_var)
{
struct timerlat_variables *tlat_var = this_cpu_tmr_var();
/*
* If the timerlat is enabled, but the irq handler did
* not run yet enabling timerlat_tracer, do not trace.
*/
if (!tlat_var->tracing_thread) {
osn_var->softirq.arrival_time = 0;
osn_var->softirq.delta_start = 0;
return 0;
}
return 1;
}
static inline int timerlat_thread_exit(struct osnoise_variables *osn_var)
{
struct timerlat_variables *tlat_var = this_cpu_tmr_var();
/*
* If the timerlat is enabled, but the irq handler did
* not run yet enabling timerlat_tracer, do not trace.
*/
if (!tlat_var->tracing_thread) {
osn_var->thread.delta_start = 0;
osn_var->thread.arrival_time = 0;
return 0;
}
return 1;
}
#else /* CONFIG_TIMERLAT_TRACER */
static inline bool timerlat_enabled(void)
{
return false;
}
static inline int timerlat_softirq_exit(struct osnoise_variables *osn_var)
{
return 1;
}
static inline int timerlat_thread_exit(struct osnoise_variables *osn_var)
{
return 1;
}
#endif
#ifdef CONFIG_PREEMPT_RT
/*
* Print the osnoise header info.
*/
static void print_osnoise_headers(struct seq_file *s)
{
if (osnoise_data.tainted)
seq_puts(s, "# osnoise is tainted!\n");
seq_puts(s, "# _-------=> irqs-off\n");
seq_puts(s, "# / _------=> need-resched\n");
seq_puts(s, "# | / _-----=> need-resched-lazy\n");
seq_puts(s, "# || / _----=> hardirq/softirq\n");
seq_puts(s, "# ||| / _---=> preempt-depth\n");
seq_puts(s, "# |||| / _--=> preempt-lazy-depth\n");
seq_puts(s, "# ||||| / _-=> migrate-disable\n");
seq_puts(s, "# |||||| / ");
seq_puts(s, " MAX\n");
seq_puts(s, "# ||||| / ");
seq_puts(s, " SINGLE Interference counters:\n");
seq_puts(s, "# ||||||| RUNTIME ");
seq_puts(s, " NOISE %% OF CPU NOISE +-----------------------------+\n");
seq_puts(s, "# TASK-PID CPU# ||||||| TIMESTAMP IN US ");
seq_puts(s, " IN US AVAILABLE IN US HW NMI IRQ SIRQ THREAD\n");
seq_puts(s, "# | | | ||||||| | | ");
seq_puts(s, " | | | | | | | |\n");
}
#else /* CONFIG_PREEMPT_RT */
static void print_osnoise_headers(struct seq_file *s)
{
if (osnoise_data.tainted)
seq_puts(s, "# osnoise is tainted!\n");
seq_puts(s, "# _-----=> irqs-off\n");
seq_puts(s, "# / _----=> need-resched\n");
seq_puts(s, "# | / _---=> hardirq/softirq\n");
seq_puts(s, "# || / _--=> preempt-depth\n");
seq_puts(s, "# ||| / _-=> migrate-disable ");
seq_puts(s, " MAX\n");
seq_puts(s, "# |||| / delay ");
seq_puts(s, " SINGLE Interference counters:\n");
seq_puts(s, "# ||||| RUNTIME ");
seq_puts(s, " NOISE %% OF CPU NOISE +-----------------------------+\n");
seq_puts(s, "# TASK-PID CPU# ||||| TIMESTAMP IN US ");
seq_puts(s, " IN US AVAILABLE IN US HW NMI IRQ SIRQ THREAD\n");
seq_puts(s, "# | | | ||||| | | ");
seq_puts(s, " | | | | | | | |\n");
}
#endif /* CONFIG_PREEMPT_RT */
/*
* osnoise_taint - report an osnoise error.
*/
#define osnoise_taint(msg) ({ \
struct osnoise_instance *inst; \
struct trace_buffer *buffer; \
\
rcu_read_lock(); \
list_for_each_entry_rcu(inst, &osnoise_instances, list) { \
buffer = inst->tr->array_buffer.buffer; \
trace_array_printk_buf(buffer, _THIS_IP_, msg); \
} \
rcu_read_unlock(); \
osnoise_data.tainted = true; \
})
/*
* Record an osnoise_sample into the tracer buffer.
*/
static void
__trace_osnoise_sample(struct osnoise_sample *sample, struct trace_buffer *buffer)
{
struct trace_event_call *call = &event_osnoise;
struct ring_buffer_event *event;
struct osnoise_entry *entry;
event = trace_buffer_lock_reserve(buffer, TRACE_OSNOISE, sizeof(*entry),
tracing_gen_ctx());
if (!event)
return;
entry = ring_buffer_event_data(event);
entry->runtime = sample->runtime;
entry->noise = sample->noise;
entry->max_sample = sample->max_sample;
entry->hw_count = sample->hw_count;
entry->nmi_count = sample->nmi_count;
entry->irq_count = sample->irq_count;
entry->softirq_count = sample->softirq_count;
entry->thread_count = sample->thread_count;
if (!call_filter_check_discard(call, entry, buffer, event))
trace_buffer_unlock_commit_nostack(buffer, event);
}
/*
* Record an osnoise_sample on all osnoise instances.
*/
static void trace_osnoise_sample(struct osnoise_sample *sample)
{
struct osnoise_instance *inst;
struct trace_buffer *buffer;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
buffer = inst->tr->array_buffer.buffer;
__trace_osnoise_sample(sample, buffer);
}
rcu_read_unlock();
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* Print the timerlat header info.
*/
#ifdef CONFIG_PREEMPT_RT
static void print_timerlat_headers(struct seq_file *s)
{
seq_puts(s, "# _-------=> irqs-off\n");
seq_puts(s, "# / _------=> need-resched\n");
seq_puts(s, "# | / _-----=> need-resched-lazy\n");
seq_puts(s, "# || / _----=> hardirq/softirq\n");
seq_puts(s, "# ||| / _---=> preempt-depth\n");
seq_puts(s, "# |||| / _--=> preempt-lazy-depth\n");
seq_puts(s, "# ||||| / _-=> migrate-disable\n");
seq_puts(s, "# |||||| /\n");
seq_puts(s, "# ||||||| ACTIVATION\n");
seq_puts(s, "# TASK-PID CPU# ||||||| TIMESTAMP ID ");
seq_puts(s, " CONTEXT LATENCY\n");
seq_puts(s, "# | | | ||||||| | | ");
seq_puts(s, " | |\n");
}
#else /* CONFIG_PREEMPT_RT */
static void print_timerlat_headers(struct seq_file *s)
{
seq_puts(s, "# _-----=> irqs-off\n");
seq_puts(s, "# / _----=> need-resched\n");
seq_puts(s, "# | / _---=> hardirq/softirq\n");
seq_puts(s, "# || / _--=> preempt-depth\n");
seq_puts(s, "# ||| / _-=> migrate-disable\n");
seq_puts(s, "# |||| / delay\n");
seq_puts(s, "# ||||| ACTIVATION\n");
seq_puts(s, "# TASK-PID CPU# ||||| TIMESTAMP ID ");
seq_puts(s, " CONTEXT LATENCY\n");
seq_puts(s, "# | | | ||||| | | ");
seq_puts(s, " | |\n");
}
#endif /* CONFIG_PREEMPT_RT */
static void
__trace_timerlat_sample(struct timerlat_sample *sample, struct trace_buffer *buffer)
{
struct trace_event_call *call = &event_osnoise;
struct ring_buffer_event *event;
struct timerlat_entry *entry;
event = trace_buffer_lock_reserve(buffer, TRACE_TIMERLAT, sizeof(*entry),
tracing_gen_ctx());
if (!event)
return;
entry = ring_buffer_event_data(event);
entry->seqnum = sample->seqnum;
entry->context = sample->context;
entry->timer_latency = sample->timer_latency;
if (!call_filter_check_discard(call, entry, buffer, event))
trace_buffer_unlock_commit_nostack(buffer, event);
}
/*
* Record an timerlat_sample into the tracer buffer.
*/
static void trace_timerlat_sample(struct timerlat_sample *sample)
{
struct osnoise_instance *inst;
struct trace_buffer *buffer;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
buffer = inst->tr->array_buffer.buffer;
__trace_timerlat_sample(sample, buffer);
}
rcu_read_unlock();
}
#ifdef CONFIG_STACKTRACE
#define MAX_CALLS 256
/*
* Stack trace will take place only at IRQ level, so, no need
* to control nesting here.
*/
struct trace_stack {
int stack_size;
int nr_entries;
unsigned long calls[MAX_CALLS];
};
static DEFINE_PER_CPU(struct trace_stack, trace_stack);
/*
* timerlat_save_stack - save a stack trace without printing
*
* Save the current stack trace without printing. The
* stack will be printed later, after the end of the measurement.
*/
static void timerlat_save_stack(int skip)
{
unsigned int size, nr_entries;
struct trace_stack *fstack;
fstack = this_cpu_ptr(&trace_stack);
size = ARRAY_SIZE(fstack->calls);
nr_entries = stack_trace_save(fstack->calls, size, skip);
fstack->stack_size = nr_entries * sizeof(unsigned long);
fstack->nr_entries = nr_entries;
return;
}
static void
__timerlat_dump_stack(struct trace_buffer *buffer, struct trace_stack *fstack, unsigned int size)
{
struct trace_event_call *call = &event_osnoise;
struct ring_buffer_event *event;
struct stack_entry *entry;
event = trace_buffer_lock_reserve(buffer, TRACE_STACK, sizeof(*entry) + size,
tracing_gen_ctx());
if (!event)
return;
entry = ring_buffer_event_data(event);
memcpy(&entry->caller, fstack->calls, size);
entry->size = fstack->nr_entries;
if (!call_filter_check_discard(call, entry, buffer, event))
trace_buffer_unlock_commit_nostack(buffer, event);
}
/*
* timerlat_dump_stack - dump a stack trace previously saved
*/
static void timerlat_dump_stack(u64 latency)
{
struct osnoise_instance *inst;
struct trace_buffer *buffer;
struct trace_stack *fstack;
unsigned int size;
/*
* trace only if latency > print_stack config, if enabled.
*/
if (!osnoise_data.print_stack || osnoise_data.print_stack > latency)
return;
preempt_disable_notrace();
fstack = this_cpu_ptr(&trace_stack);
size = fstack->stack_size;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
buffer = inst->tr->array_buffer.buffer;
__timerlat_dump_stack(buffer, fstack, size);
}
rcu_read_unlock();
preempt_enable_notrace();
}
#else /* CONFIG_STACKTRACE */
#define timerlat_dump_stack(u64 latency) do {} while (0)
#define timerlat_save_stack(a) do {} while (0)
#endif /* CONFIG_STACKTRACE */
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* Macros to encapsulate the time capturing infrastructure.
*/
#define time_get() trace_clock_local()
#define time_to_us(x) div_u64(x, 1000)
#define time_sub(a, b) ((a) - (b))
/*
* cond_move_irq_delta_start - Forward the delta_start of a running IRQ
*
* If an IRQ is preempted by an NMI, its delta_start is pushed forward
* to discount the NMI interference.
*
* See get_int_safe_duration().
*/
static inline void
cond_move_irq_delta_start(struct osnoise_variables *osn_var, u64 duration)
{
if (osn_var->irq.delta_start)
osn_var->irq.delta_start += duration;
}
#ifndef CONFIG_PREEMPT_RT
/*
* cond_move_softirq_delta_start - Forward the delta_start of a running softirq.
*
* If a softirq is preempted by an IRQ or NMI, its delta_start is pushed
* forward to discount the interference.
*
* See get_int_safe_duration().
*/
static inline void
cond_move_softirq_delta_start(struct osnoise_variables *osn_var, u64 duration)
{
if (osn_var->softirq.delta_start)
osn_var->softirq.delta_start += duration;
}
#else /* CONFIG_PREEMPT_RT */
#define cond_move_softirq_delta_start(osn_var, duration) do {} while (0)
#endif
/*
* cond_move_thread_delta_start - Forward the delta_start of a running thread
*
* If a noisy thread is preempted by an softirq, IRQ or NMI, its delta_start
* is pushed forward to discount the interference.
*
* See get_int_safe_duration().
*/
static inline void
cond_move_thread_delta_start(struct osnoise_variables *osn_var, u64 duration)
{
if (osn_var->thread.delta_start)
osn_var->thread.delta_start += duration;
}
/*
* get_int_safe_duration - Get the duration of a window
*
* The irq, softirq and thread varaibles need to have its duration without
* the interference from higher priority interrupts. Instead of keeping a
* variable to discount the interrupt interference from these variables, the
* starting time of these variables are pushed forward with the interrupt's
* duration. In this way, a single variable is used to:
*
* - Know if a given window is being measured.
* - Account its duration.
* - Discount the interference.
*
* To avoid getting inconsistent values, e.g.,:
*
* now = time_get()
* ---> interrupt!
* delta_start -= int duration;
* <---
* duration = now - delta_start;
*
* result: negative duration if the variable duration before the
* interrupt was smaller than the interrupt execution.
*
* A counter of interrupts is used. If the counter increased, try
* to capture an interference safe duration.
*/
static inline s64
get_int_safe_duration(struct osnoise_variables *osn_var, u64 *delta_start)
{
u64 int_counter, now;
s64 duration;
do {
int_counter = local_read(&osn_var->int_counter);
/* synchronize with interrupts */
barrier();
now = time_get();
duration = (now - *delta_start);
/* synchronize with interrupts */
barrier();
} while (int_counter != local_read(&osn_var->int_counter));
/*
* This is an evidence of race conditions that cause
* a value to be "discounted" too much.
*/
if (duration < 0)
osnoise_taint("Negative duration!\n");
*delta_start = 0;
return duration;
}
/*
*
* set_int_safe_time - Save the current time on *time, aware of interference
*
* Get the time, taking into consideration a possible interference from
* higher priority interrupts.
*
* See get_int_safe_duration() for an explanation.
*/
static u64
set_int_safe_time(struct osnoise_variables *osn_var, u64 *time)
{
u64 int_counter;
do {
int_counter = local_read(&osn_var->int_counter);
/* synchronize with interrupts */
barrier();
*time = time_get();
/* synchronize with interrupts */
barrier();
} while (int_counter != local_read(&osn_var->int_counter));
return int_counter;
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* copy_int_safe_time - Copy *src into *desc aware of interference
*/
static u64
copy_int_safe_time(struct osnoise_variables *osn_var, u64 *dst, u64 *src)
{
u64 int_counter;
do {
int_counter = local_read(&osn_var->int_counter);
/* synchronize with interrupts */
barrier();
*dst = *src;
/* synchronize with interrupts */
barrier();
} while (int_counter != local_read(&osn_var->int_counter));
return int_counter;
}
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* trace_osnoise_callback - NMI entry/exit callback
*
* This function is called at the entry and exit NMI code. The bool enter
* distinguishes between either case. This function is used to note a NMI
* occurrence, compute the noise caused by the NMI, and to remove the noise
* it is potentially causing on other interference variables.
*/
void trace_osnoise_callback(bool enter)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
u64 duration;
if (!osn_var->sampling)
return;
/*
* Currently trace_clock_local() calls sched_clock() and the
* generic version is not NMI safe.
*/
if (!IS_ENABLED(CONFIG_GENERIC_SCHED_CLOCK)) {
if (enter) {
osn_var->nmi.delta_start = time_get();
local_inc(&osn_var->int_counter);
} else {
duration = time_get() - osn_var->nmi.delta_start;
trace_nmi_noise(osn_var->nmi.delta_start, duration);
cond_move_irq_delta_start(osn_var, duration);
cond_move_softirq_delta_start(osn_var, duration);
cond_move_thread_delta_start(osn_var, duration);
}
}
if (enter)
osn_var->nmi.count++;
}
/*
* osnoise_trace_irq_entry - Note the starting of an IRQ
*
* Save the starting time of an IRQ. As IRQs are non-preemptive to other IRQs,
* it is safe to use a single variable (ons_var->irq) to save the statistics.
* The arrival_time is used to report... the arrival time. The delta_start
* is used to compute the duration at the IRQ exit handler. See
* cond_move_irq_delta_start().
*/
void osnoise_trace_irq_entry(int id)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
if (!osn_var->sampling)
return;
/*
* This value will be used in the report, but not to compute
* the execution time, so it is safe to get it unsafe.
*/
osn_var->irq.arrival_time = time_get();
set_int_safe_time(osn_var, &osn_var->irq.delta_start);
osn_var->irq.count++;
local_inc(&osn_var->int_counter);
}
/*
* osnoise_irq_exit - Note the end of an IRQ, sava data and trace
*
* Computes the duration of the IRQ noise, and trace it. Also discounts the
* interference from other sources of noise could be currently being accounted.
*/
void osnoise_trace_irq_exit(int id, const char *desc)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
s64 duration;
if (!osn_var->sampling)
return;
duration = get_int_safe_duration(osn_var, &osn_var->irq.delta_start);
trace_irq_noise(id, desc, osn_var->irq.arrival_time, duration);
osn_var->irq.arrival_time = 0;
cond_move_softirq_delta_start(osn_var, duration);
cond_move_thread_delta_start(osn_var, duration);
}
/*
* trace_irqentry_callback - Callback to the irq:irq_entry traceevent
*
* Used to note the starting of an IRQ occurece.
*/
static void trace_irqentry_callback(void *data, int irq,
struct irqaction *action)
{
osnoise_trace_irq_entry(irq);
}
/*
* trace_irqexit_callback - Callback to the irq:irq_exit traceevent
*
* Used to note the end of an IRQ occurece.
*/
static void trace_irqexit_callback(void *data, int irq,
struct irqaction *action, int ret)
{
osnoise_trace_irq_exit(irq, action->name);
}
/*
* arch specific register function.
*/
int __weak osnoise_arch_register(void)
{
return 0;
}
/*
* arch specific unregister function.
*/
void __weak osnoise_arch_unregister(void)
{
return;
}
/*
* hook_irq_events - Hook IRQ handling events
*
* This function hooks the IRQ related callbacks to the respective trace
* events.
*/
static int hook_irq_events(void)
{
int ret;
ret = register_trace_irq_handler_entry(trace_irqentry_callback, NULL);
if (ret)
goto out_err;
ret = register_trace_irq_handler_exit(trace_irqexit_callback, NULL);
if (ret)
goto out_unregister_entry;
ret = osnoise_arch_register();
if (ret)
goto out_irq_exit;
return 0;
out_irq_exit:
unregister_trace_irq_handler_exit(trace_irqexit_callback, NULL);
out_unregister_entry:
unregister_trace_irq_handler_entry(trace_irqentry_callback, NULL);
out_err:
return -EINVAL;
}
/*
* unhook_irq_events - Unhook IRQ handling events
*
* This function unhooks the IRQ related callbacks to the respective trace
* events.
*/
static void unhook_irq_events(void)
{
osnoise_arch_unregister();
unregister_trace_irq_handler_exit(trace_irqexit_callback, NULL);
unregister_trace_irq_handler_entry(trace_irqentry_callback, NULL);
}
#ifndef CONFIG_PREEMPT_RT
/*
* trace_softirq_entry_callback - Note the starting of a softirq
*
* Save the starting time of a softirq. As softirqs are non-preemptive to
* other softirqs, it is safe to use a single variable (ons_var->softirq)
* to save the statistics. The arrival_time is used to report... the
* arrival time. The delta_start is used to compute the duration at the
* softirq exit handler. See cond_move_softirq_delta_start().
*/
static void trace_softirq_entry_callback(void *data, unsigned int vec_nr)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
if (!osn_var->sampling)
return;
/*
* This value will be used in the report, but not to compute
* the execution time, so it is safe to get it unsafe.
*/
osn_var->softirq.arrival_time = time_get();
set_int_safe_time(osn_var, &osn_var->softirq.delta_start);
osn_var->softirq.count++;
local_inc(&osn_var->int_counter);
}
/*
* trace_softirq_exit_callback - Note the end of an softirq
*
* Computes the duration of the softirq noise, and trace it. Also discounts the
* interference from other sources of noise could be currently being accounted.
*/
static void trace_softirq_exit_callback(void *data, unsigned int vec_nr)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
s64 duration;
if (!osn_var->sampling)
return;
if (unlikely(timerlat_enabled()))
if (!timerlat_softirq_exit(osn_var))
return;
duration = get_int_safe_duration(osn_var, &osn_var->softirq.delta_start);
trace_softirq_noise(vec_nr, osn_var->softirq.arrival_time, duration);
cond_move_thread_delta_start(osn_var, duration);
osn_var->softirq.arrival_time = 0;
}
/*
* hook_softirq_events - Hook softirq handling events
*
* This function hooks the softirq related callbacks to the respective trace
* events.
*/
static int hook_softirq_events(void)
{
int ret;
ret = register_trace_softirq_entry(trace_softirq_entry_callback, NULL);
if (ret)
goto out_err;
ret = register_trace_softirq_exit(trace_softirq_exit_callback, NULL);
if (ret)
goto out_unreg_entry;
return 0;
out_unreg_entry:
unregister_trace_softirq_entry(trace_softirq_entry_callback, NULL);
out_err:
return -EINVAL;
}
/*
* unhook_softirq_events - Unhook softirq handling events
*
* This function hooks the softirq related callbacks to the respective trace
* events.
*/
static void unhook_softirq_events(void)
{
unregister_trace_softirq_entry(trace_softirq_entry_callback, NULL);
unregister_trace_softirq_exit(trace_softirq_exit_callback, NULL);
}
#else /* CONFIG_PREEMPT_RT */
/*
* softirq are threads on the PREEMPT_RT mode.
*/
static int hook_softirq_events(void)
{
return 0;
}
static void unhook_softirq_events(void)
{
}
#endif
/*
* thread_entry - Record the starting of a thread noise window
*
* It saves the context switch time for a noisy thread, and increments
* the interference counters.
*/
static void
thread_entry(struct osnoise_variables *osn_var, struct task_struct *t)
{
if (!osn_var->sampling)
return;
/*
* The arrival time will be used in the report, but not to compute
* the execution time, so it is safe to get it unsafe.
*/
osn_var->thread.arrival_time = time_get();
set_int_safe_time(osn_var, &osn_var->thread.delta_start);
osn_var->thread.count++;
local_inc(&osn_var->int_counter);
}
/*
* thread_exit - Report the end of a thread noise window
*
* It computes the total noise from a thread, tracing if needed.
*/
static void
thread_exit(struct osnoise_variables *osn_var, struct task_struct *t)
{
s64 duration;
if (!osn_var->sampling)
return;
if (unlikely(timerlat_enabled()))
if (!timerlat_thread_exit(osn_var))
return;
duration = get_int_safe_duration(osn_var, &osn_var->thread.delta_start);
trace_thread_noise(t, osn_var->thread.arrival_time, duration);
osn_var->thread.arrival_time = 0;
}
/*
* trace_sched_switch - sched:sched_switch trace event handler
*
* This function is hooked to the sched:sched_switch trace event, and it is
* used to record the beginning and to report the end of a thread noise window.
*/
static void
trace_sched_switch_callback(void *data, bool preempt,
struct task_struct *p,
struct task_struct *n,
unsigned int prev_state)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
if (p->pid != osn_var->pid)
thread_exit(osn_var, p);
if (n->pid != osn_var->pid)
thread_entry(osn_var, n);
}
/*
* hook_thread_events - Hook the insturmentation for thread noise
*
* Hook the osnoise tracer callbacks to handle the noise from other
* threads on the necessary kernel events.
*/
static int hook_thread_events(void)
{
int ret;
ret = register_trace_sched_switch(trace_sched_switch_callback, NULL);
if (ret)
return -EINVAL;
return 0;
}
/*
* unhook_thread_events - *nhook the insturmentation for thread noise
*
* Unook the osnoise tracer callbacks to handle the noise from other
* threads on the necessary kernel events.
*/
static void unhook_thread_events(void)
{
unregister_trace_sched_switch(trace_sched_switch_callback, NULL);
}
/*
* save_osn_sample_stats - Save the osnoise_sample statistics
*
* Save the osnoise_sample statistics before the sampling phase. These
* values will be used later to compute the diff betwneen the statistics
* before and after the osnoise sampling.
*/
static void
save_osn_sample_stats(struct osnoise_variables *osn_var, struct osnoise_sample *s)
{
s->nmi_count = osn_var->nmi.count;
s->irq_count = osn_var->irq.count;
s->softirq_count = osn_var->softirq.count;
s->thread_count = osn_var->thread.count;
}
/*
* diff_osn_sample_stats - Compute the osnoise_sample statistics
*
* After a sample period, compute the difference on the osnoise_sample
* statistics. The struct osnoise_sample *s contains the statistics saved via
* save_osn_sample_stats() before the osnoise sampling.
*/
static void
diff_osn_sample_stats(struct osnoise_variables *osn_var, struct osnoise_sample *s)
{
s->nmi_count = osn_var->nmi.count - s->nmi_count;
s->irq_count = osn_var->irq.count - s->irq_count;
s->softirq_count = osn_var->softirq.count - s->softirq_count;
s->thread_count = osn_var->thread.count - s->thread_count;
}
/*
* osnoise_stop_tracing - Stop tracing and the tracer.
*/
static __always_inline void osnoise_stop_tracing(void)
{
struct osnoise_instance *inst;
struct trace_array *tr;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
tr = inst->tr;
trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
"stop tracing hit on cpu %d\n", smp_processor_id());
tracer_tracing_off(tr);
}
rcu_read_unlock();
}
/*
* notify_new_max_latency - Notify a new max latency via fsnotify interface.
*/
static void notify_new_max_latency(u64 latency)
{
struct osnoise_instance *inst;
struct trace_array *tr;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
tr = inst->tr;
if (tr->max_latency < latency) {
tr->max_latency = latency;
latency_fsnotify(tr);
}
}
rcu_read_unlock();
}
/*
* run_osnoise - Sample the time and look for osnoise
*
* Used to capture the time, looking for potential osnoise latency repeatedly.
* Different from hwlat_detector, it is called with preemption and interrupts
* enabled. This allows irqs, softirqs and threads to run, interfering on the
* osnoise sampling thread, as they would do with a regular thread.
*/
static int run_osnoise(void)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
u64 start, sample, last_sample;
u64 last_int_count, int_count;
s64 noise = 0, max_noise = 0;
s64 total, last_total = 0;
struct osnoise_sample s;
unsigned int threshold;
u64 runtime, stop_in;
u64 sum_noise = 0;
int hw_count = 0;
int ret = -1;
/*
* Considers the current thread as the workload.
*/
osn_var->pid = current->pid;
/*
* Save the current stats for the diff
*/
save_osn_sample_stats(osn_var, &s);
/*
* if threshold is 0, use the default value of 5 us.
*/
threshold = tracing_thresh ? : 5000;
/*
* Make sure NMIs see sampling first
*/
osn_var->sampling = true;
barrier();
/*
* Transform the *_us config to nanoseconds to avoid the
* division on the main loop.
*/
runtime = osnoise_data.sample_runtime * NSEC_PER_USEC;
stop_in = osnoise_data.stop_tracing * NSEC_PER_USEC;
/*
* Start timestemp
*/
start = time_get();
/*
* "previous" loop.
*/
last_int_count = set_int_safe_time(osn_var, &last_sample);
do {
/*
* Get sample!
*/
int_count = set_int_safe_time(osn_var, &sample);
noise = time_sub(sample, last_sample);
/*
* This shouldn't happen.
*/
if (noise < 0) {
osnoise_taint("negative noise!");
goto out;
}
/*
* Sample runtime.
*/
total = time_sub(sample, start);
/*
* Check for possible overflows.
*/
if (total < last_total) {
osnoise_taint("total overflow!");
break;
}
last_total = total;
if (noise >= threshold) {
int interference = int_count - last_int_count;
if (noise > max_noise)
max_noise = noise;
if (!interference)
hw_count++;
sum_noise += noise;
trace_sample_threshold(last_sample, noise, interference);
if (osnoise_data.stop_tracing)
if (noise > stop_in)
osnoise_stop_tracing();
}
/*
* In some cases, notably when running on a nohz_full CPU with
* a stopped tick PREEMPT_RCU has no way to account for QSs.
* This will eventually cause unwarranted noise as PREEMPT_RCU
* will force preemption as the means of ending the current
* grace period. We avoid this problem by calling
* rcu_momentary_dyntick_idle(), which performs a zero duration
* EQS allowing PREEMPT_RCU to end the current grace period.
* This call shouldn't be wrapped inside an RCU critical
* section.
*
* Note that in non PREEMPT_RCU kernels QSs are handled through
* cond_resched()
*/
if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
local_irq_disable();
rcu_momentary_dyntick_idle();
local_irq_enable();
}
/*
* For the non-preemptive kernel config: let threads runs, if
* they so wish.
*/
cond_resched();
last_sample = sample;
last_int_count = int_count;
} while (total < runtime && !kthread_should_stop());
/*
* Finish the above in the view for interrupts.
*/
barrier();
osn_var->sampling = false;
/*
* Make sure sampling data is no longer updated.
*/
barrier();
/*
* Save noise info.
*/
s.noise = time_to_us(sum_noise);
s.runtime = time_to_us(total);
s.max_sample = time_to_us(max_noise);
s.hw_count = hw_count;
/* Save interference stats info */
diff_osn_sample_stats(osn_var, &s);
trace_osnoise_sample(&s);
notify_new_max_latency(max_noise);
if (osnoise_data.stop_tracing_total)
if (s.noise > osnoise_data.stop_tracing_total)
osnoise_stop_tracing();
return 0;
out:
return ret;
}
static struct cpumask osnoise_cpumask;
static struct cpumask save_cpumask;
/*
* osnoise_sleep - sleep until the next period
*/
static void osnoise_sleep(void)
{
u64 interval;
ktime_t wake_time;
mutex_lock(&interface_lock);
interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
mutex_unlock(&interface_lock);
/*
* differently from hwlat_detector, the osnoise tracer can run
* without a pause because preemption is on.
*/
if (!interval) {
/* Let synchronize_rcu_tasks() make progress */
cond_resched_tasks_rcu_qs();
return;
}
wake_time = ktime_add_us(ktime_get(), interval);
__set_current_state(TASK_INTERRUPTIBLE);
while (schedule_hrtimeout_range(&wake_time, 0, HRTIMER_MODE_ABS)) {
if (kthread_should_stop())
break;
}
}
/*
* osnoise_main - The osnoise detection kernel thread
*
* Calls run_osnoise() function to measure the osnoise for the configured runtime,
* every period.
*/
static int osnoise_main(void *data)
{
while (!kthread_should_stop()) {
run_osnoise();
osnoise_sleep();
}
return 0;
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* timerlat_irq - hrtimer handler for timerlat.
*/
static enum hrtimer_restart timerlat_irq(struct hrtimer *timer)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
struct timerlat_variables *tlat;
struct timerlat_sample s;
u64 now;
u64 diff;
/*
* I am not sure if the timer was armed for this CPU. So, get
* the timerlat struct from the timer itself, not from this
* CPU.
*/
tlat = container_of(timer, struct timerlat_variables, timer);
now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer));
/*
* Enable the osnoise: events for thread an softirq.
*/
tlat->tracing_thread = true;
osn_var->thread.arrival_time = time_get();
/*
* A hardirq is running: the timer IRQ. It is for sure preempting
* a thread, and potentially preempting a softirq.
*
* At this point, it is not interesting to know the duration of the
* preempted thread (and maybe softirq), but how much time they will
* delay the beginning of the execution of the timer thread.
*
* To get the correct (net) delay added by the softirq, its delta_start
* is set as the IRQ one. In this way, at the return of the IRQ, the delta
* start of the sofitrq will be zeroed, accounting then only the time
* after that.
*
* The thread follows the same principle. However, if a softirq is
* running, the thread needs to receive the softirq delta_start. The
* reason being is that the softirq will be the last to be unfolded,
* resseting the thread delay to zero.
*
* The PREEMPT_RT is a special case, though. As softirqs run as threads
* on RT, moving the thread is enough.
*/
if (!IS_ENABLED(CONFIG_PREEMPT_RT) && osn_var->softirq.delta_start) {
copy_int_safe_time(osn_var, &osn_var->thread.delta_start,
&osn_var->softirq.delta_start);
copy_int_safe_time(osn_var, &osn_var->softirq.delta_start,
&osn_var->irq.delta_start);
} else {
copy_int_safe_time(osn_var, &osn_var->thread.delta_start,
&osn_var->irq.delta_start);
}
/*
* Compute the current time with the expected time.
*/
diff = now - tlat->abs_period;
tlat->count++;
s.seqnum = tlat->count;
s.timer_latency = diff;
s.context = IRQ_CONTEXT;
trace_timerlat_sample(&s);
if (osnoise_data.stop_tracing) {
if (time_to_us(diff) >= osnoise_data.stop_tracing) {
/*
* At this point, if stop_tracing is set and <= print_stack,
* print_stack is set and would be printed in the thread handler.
*
* Thus, print the stack trace as it is helpful to define the
* root cause of an IRQ latency.
*/
if (osnoise_data.stop_tracing <= osnoise_data.print_stack) {
timerlat_save_stack(0);
timerlat_dump_stack(time_to_us(diff));
}
osnoise_stop_tracing();
notify_new_max_latency(diff);
return HRTIMER_NORESTART;
}
}
wake_up_process(tlat->kthread);
if (osnoise_data.print_stack)
timerlat_save_stack(0);
return HRTIMER_NORESTART;
}
/*
* wait_next_period - Wait for the next period for timerlat
*/
static int wait_next_period(struct timerlat_variables *tlat)
{
ktime_t next_abs_period, now;
u64 rel_period = osnoise_data.timerlat_period * 1000;
now = hrtimer_cb_get_time(&tlat->timer);
next_abs_period = ns_to_ktime(tlat->abs_period + rel_period);
/*
* Save the next abs_period.
*/
tlat->abs_period = (u64) ktime_to_ns(next_abs_period);
/*
* If the new abs_period is in the past, skip the activation.
*/
while (ktime_compare(now, next_abs_period) > 0) {
next_abs_period = ns_to_ktime(tlat->abs_period + rel_period);
tlat->abs_period = (u64) ktime_to_ns(next_abs_period);
}
set_current_state(TASK_INTERRUPTIBLE);
hrtimer_start(&tlat->timer, next_abs_period, HRTIMER_MODE_ABS_PINNED_HARD);
schedule();
return 1;
}
/*
* timerlat_main- Timerlat main
*/
static int timerlat_main(void *data)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
struct timerlat_variables *tlat = this_cpu_tmr_var();
struct timerlat_sample s;
struct sched_param sp;
u64 now, diff;
/*
* Make the thread RT, that is how cyclictest is usually used.
*/
sp.sched_priority = DEFAULT_TIMERLAT_PRIO;
sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
tlat->count = 0;
tlat->tracing_thread = false;
hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
tlat->timer.function = timerlat_irq;
tlat->kthread = current;
osn_var->pid = current->pid;
/*
* Anotate the arrival time.
*/
tlat->abs_period = hrtimer_cb_get_time(&tlat->timer);
wait_next_period(tlat);
osn_var->sampling = 1;
while (!kthread_should_stop()) {
now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer));
diff = now - tlat->abs_period;
s.seqnum = tlat->count;
s.timer_latency = diff;
s.context = THREAD_CONTEXT;
trace_timerlat_sample(&s);
timerlat_dump_stack(time_to_us(diff));
tlat->tracing_thread = false;
if (osnoise_data.stop_tracing_total)
if (time_to_us(diff) >= osnoise_data.stop_tracing_total)
osnoise_stop_tracing();
wait_next_period(tlat);
}
hrtimer_cancel(&tlat->timer);
return 0;
}
#else /* CONFIG_TIMERLAT_TRACER */
static int timerlat_main(void *data)
{
return 0;
}
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* stop_kthread - stop a workload thread
*/
static void stop_kthread(unsigned int cpu)
{
struct task_struct *kthread;
kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
if (kthread)
kthread_stop(kthread);
per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
}
/*
* stop_per_cpu_kthread - Stop per-cpu threads
*
* Stop the osnoise sampling htread. Use this on unload and at system
* shutdown.
*/
static void stop_per_cpu_kthreads(void)
{
int cpu;
cpus_read_lock();
for_each_online_cpu(cpu)
stop_kthread(cpu);
cpus_read_unlock();
}
/*
* start_kthread - Start a workload tread
*/
static int start_kthread(unsigned int cpu)
{
struct task_struct *kthread;
void *main = osnoise_main;
char comm[24];
if (timerlat_enabled()) {
snprintf(comm, 24, "timerlat/%d", cpu);
main = timerlat_main;
} else {
snprintf(comm, 24, "osnoise/%d", cpu);
}
kthread = kthread_run_on_cpu(main, NULL, cpu, comm);
if (IS_ERR(kthread)) {
pr_err(BANNER "could not start sampling thread\n");
stop_per_cpu_kthreads();
return -ENOMEM;
}
per_cpu(per_cpu_osnoise_var, cpu).kthread = kthread;
return 0;
}
/*
* start_per_cpu_kthread - Kick off per-cpu osnoise sampling kthreads
*
* This starts the kernel thread that will look for osnoise on many
* cpus.
*/
static int start_per_cpu_kthreads(void)
{
struct cpumask *current_mask = &save_cpumask;
int retval = 0;
int cpu;
cpus_read_lock();
/*
* Run only on online CPUs in which osnoise is allowed to run.
*/
cpumask_and(current_mask, cpu_online_mask, &osnoise_cpumask);
for_each_possible_cpu(cpu)
per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
for_each_cpu(cpu, current_mask) {
retval = start_kthread(cpu);
if (retval) {
cpus_read_unlock();
stop_per_cpu_kthreads();
return retval;
}
}
cpus_read_unlock();
return retval;
}
#ifdef CONFIG_HOTPLUG_CPU
static void osnoise_hotplug_workfn(struct work_struct *dummy)
{
unsigned int cpu = smp_processor_id();
mutex_lock(&trace_types_lock);
if (!osnoise_has_registered_instances())
goto out_unlock_trace;
mutex_lock(&interface_lock);
cpus_read_lock();
if (!cpumask_test_cpu(cpu, &osnoise_cpumask))
goto out_unlock;
start_kthread(cpu);
out_unlock:
cpus_read_unlock();
mutex_unlock(&interface_lock);
out_unlock_trace:
mutex_unlock(&trace_types_lock);
}
static DECLARE_WORK(osnoise_hotplug_work, osnoise_hotplug_workfn);
/*
* osnoise_cpu_init - CPU hotplug online callback function
*/
static int osnoise_cpu_init(unsigned int cpu)
{
schedule_work_on(cpu, &osnoise_hotplug_work);
return 0;
}
/*
* osnoise_cpu_die - CPU hotplug offline callback function
*/
static int osnoise_cpu_die(unsigned int cpu)
{
stop_kthread(cpu);
return 0;
}
static void osnoise_init_hotplug_support(void)
{
int ret;
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "trace/osnoise:online",
osnoise_cpu_init, osnoise_cpu_die);
if (ret < 0)
pr_warn(BANNER "Error to init cpu hotplug support\n");
return;
}
#else /* CONFIG_HOTPLUG_CPU */
static void osnoise_init_hotplug_support(void)
{
return;
}
#endif /* CONFIG_HOTPLUG_CPU */
/*
* osnoise_cpus_read - Read function for reading the "cpus" file
* @filp: The active open file structure
* @ubuf: The userspace provided buffer to read value into
* @cnt: The maximum number of bytes to read
* @ppos: The current "file" position
*
* Prints the "cpus" output into the user-provided buffer.
*/
static ssize_t
osnoise_cpus_read(struct file *filp, char __user *ubuf, size_t count,
loff_t *ppos)
{
char *mask_str;
int len;
mutex_lock(&interface_lock);
len = snprintf(NULL, 0, "%*pbl\n", cpumask_pr_args(&osnoise_cpumask)) + 1;
mask_str = kmalloc(len, GFP_KERNEL);
if (!mask_str) {
count = -ENOMEM;
goto out_unlock;
}
len = snprintf(mask_str, len, "%*pbl\n", cpumask_pr_args(&osnoise_cpumask));
if (len >= count) {
count = -EINVAL;
goto out_free;
}
count = simple_read_from_buffer(ubuf, count, ppos, mask_str, len);
out_free:
kfree(mask_str);
out_unlock:
mutex_unlock(&interface_lock);
return count;
}
/*
* osnoise_cpus_write - Write function for "cpus" entry
* @filp: The active open file structure
* @ubuf: The user buffer that contains the value to write
* @cnt: The maximum number of bytes to write to "file"
* @ppos: The current position in @file
*
* This function provides a write implementation for the "cpus"
* interface to the osnoise trace. By default, it lists all CPUs,
* in this way, allowing osnoise threads to run on any online CPU
* of the system. It serves to restrict the execution of osnoise to the
* set of CPUs writing via this interface. Why not use "tracing_cpumask"?
* Because the user might be interested in tracing what is running on
* other CPUs. For instance, one might run osnoise in one HT CPU
* while observing what is running on the sibling HT CPU.
*/
static ssize_t
osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
loff_t *ppos)
{
cpumask_var_t osnoise_cpumask_new;
int running, err;
char buf[256];
if (count >= 256)
return -EINVAL;
if (copy_from_user(buf, ubuf, count))
return -EFAULT;
if (!zalloc_cpumask_var(&osnoise_cpumask_new, GFP_KERNEL))
return -ENOMEM;
err = cpulist_parse(buf, osnoise_cpumask_new);
if (err)
goto err_free;
/*
* trace_types_lock is taken to avoid concurrency on start/stop.
*/
mutex_lock(&trace_types_lock);
running = osnoise_has_registered_instances();
if (running)
stop_per_cpu_kthreads();
mutex_lock(&interface_lock);
/*
* osnoise_cpumask is read by CPU hotplug operations.
*/
cpus_read_lock();
cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new);
cpus_read_unlock();
mutex_unlock(&interface_lock);
if (running)
start_per_cpu_kthreads();
mutex_unlock(&trace_types_lock);
free_cpumask_var(osnoise_cpumask_new);
return count;
err_free:
free_cpumask_var(osnoise_cpumask_new);
return err;
}
/*
* osnoise/runtime_us: cannot be greater than the period.
*/
static struct trace_min_max_param osnoise_runtime = {
.lock = &interface_lock,
.val = &osnoise_data.sample_runtime,
.max = &osnoise_data.sample_period,
.min = NULL,
};
/*
* osnoise/period_us: cannot be smaller than the runtime.
*/
static struct trace_min_max_param osnoise_period = {
.lock = &interface_lock,
.val = &osnoise_data.sample_period,
.max = NULL,
.min = &osnoise_data.sample_runtime,
};
/*
* osnoise/stop_tracing_us: no limit.
*/
static struct trace_min_max_param osnoise_stop_tracing_in = {
.lock = &interface_lock,
.val = &osnoise_data.stop_tracing,
.max = NULL,
.min = NULL,
};
/*
* osnoise/stop_tracing_total_us: no limit.
*/
static struct trace_min_max_param osnoise_stop_tracing_total = {
.lock = &interface_lock,
.val = &osnoise_data.stop_tracing_total,
.max = NULL,
.min = NULL,
};
#ifdef CONFIG_TIMERLAT_TRACER
/*
* osnoise/print_stack: print the stacktrace of the IRQ handler if the total
* latency is higher than val.
*/
static struct trace_min_max_param osnoise_print_stack = {
.lock = &interface_lock,
.val = &osnoise_data.print_stack,
.max = NULL,
.min = NULL,
};
/*
* osnoise/timerlat_period: min 100 us, max 1 s
*/
u64 timerlat_min_period = 100;
u64 timerlat_max_period = 1000000;
static struct trace_min_max_param timerlat_period = {
.lock = &interface_lock,
.val = &osnoise_data.timerlat_period,
.max = &timerlat_max_period,
.min = &timerlat_min_period,
};
#endif
static const struct file_operations cpus_fops = {
.open = tracing_open_generic,
.read = osnoise_cpus_read,
.write = osnoise_cpus_write,
.llseek = generic_file_llseek,
};
#ifdef CONFIG_TIMERLAT_TRACER
#ifdef CONFIG_STACKTRACE
static int init_timerlat_stack_tracefs(struct dentry *top_dir)
{
struct dentry *tmp;
tmp = tracefs_create_file("print_stack", TRACE_MODE_WRITE, top_dir,
&osnoise_print_stack, &trace_min_max_fops);
if (!tmp)
return -ENOMEM;
return 0;
}
#else /* CONFIG_STACKTRACE */
static int init_timerlat_stack_tracefs(struct dentry *top_dir)
{
return 0;
}
#endif /* CONFIG_STACKTRACE */
/*
* init_timerlat_tracefs - A function to initialize the timerlat interface files
*/
static int init_timerlat_tracefs(struct dentry *top_dir)
{
struct dentry *tmp;
tmp = tracefs_create_file("timerlat_period_us", TRACE_MODE_WRITE, top_dir,
&timerlat_period, &trace_min_max_fops);
if (!tmp)
return -ENOMEM;
return init_timerlat_stack_tracefs(top_dir);
}
#else /* CONFIG_TIMERLAT_TRACER */
static int init_timerlat_tracefs(struct dentry *top_dir)
{
return 0;
}
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* init_tracefs - A function to initialize the tracefs interface files
*
* This function creates entries in tracefs for "osnoise" and "timerlat".
* It creates these directories in the tracing directory, and within that
* directory the use can change and view the configs.
*/
static int init_tracefs(void)
{
struct dentry *top_dir;
struct dentry *tmp;
int ret;
ret = tracing_init_dentry();
if (ret)
return -ENOMEM;
top_dir = tracefs_create_dir("osnoise", NULL);
if (!top_dir)
return 0;
tmp = tracefs_create_file("period_us", TRACE_MODE_WRITE, top_dir,
&osnoise_period, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = tracefs_create_file("runtime_us", TRACE_MODE_WRITE, top_dir,
&osnoise_runtime, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = tracefs_create_file("stop_tracing_us", TRACE_MODE_WRITE, top_dir,
&osnoise_stop_tracing_in, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = tracefs_create_file("stop_tracing_total_us", TRACE_MODE_WRITE, top_dir,
&osnoise_stop_tracing_total, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = trace_create_file("cpus", TRACE_MODE_WRITE, top_dir, NULL, &cpus_fops);
if (!tmp)
goto err;
ret = init_timerlat_tracefs(top_dir);
if (ret)
goto err;
return 0;
err:
tracefs_remove(top_dir);
return -ENOMEM;
}
static int osnoise_hook_events(void)
{
int retval;
/*
* Trace is already hooked, we are re-enabling from
* a stop_tracing_*.
*/
if (trace_osnoise_callback_enabled)
return 0;
retval = hook_irq_events();
if (retval)
return -EINVAL;
retval = hook_softirq_events();
if (retval)
goto out_unhook_irq;
retval = hook_thread_events();
/*
* All fine!
*/
if (!retval)
return 0;
unhook_softirq_events();
out_unhook_irq:
unhook_irq_events();
return -EINVAL;
}
static void osnoise_unhook_events(void)
{
unhook_thread_events();
unhook_softirq_events();
unhook_irq_events();
}
/*
* osnoise_workload_start - start the workload and hook to events
*/
static int osnoise_workload_start(void)
{
int retval;
/*
* Instances need to be registered after calling workload
* start. Hence, if there is already an instance, the
* workload was already registered. Otherwise, this
* code is on the way to register the first instance,
* and the workload will start.
*/
if (osnoise_has_registered_instances())
return 0;
osn_var_reset_all();
retval = osnoise_hook_events();
if (retval)
return retval;
/*
* Make sure that ftrace_nmi_enter/exit() see reset values
* before enabling trace_osnoise_callback_enabled.
*/
barrier();
trace_osnoise_callback_enabled = true;
retval = start_per_cpu_kthreads();
if (retval) {
trace_osnoise_callback_enabled = false;
/*
* Make sure that ftrace_nmi_enter/exit() see
* trace_osnoise_callback_enabled as false before continuing.
*/
barrier();
osnoise_unhook_events();
return retval;
}
return 0;
}
/*
* osnoise_workload_stop - stop the workload and unhook the events
*/
static void osnoise_workload_stop(void)
{
/*
* Instances need to be unregistered before calling
* stop. Hence, if there is a registered instance, more
* than one instance is running, and the workload will not
* yet stop. Otherwise, this code is on the way to disable
* the last instance, and the workload can stop.
*/
if (osnoise_has_registered_instances())
return;
/*
* If callbacks were already disabled in a previous stop
* call, there is no need to disable then again.
*
* For instance, this happens when tracing is stopped via:
* echo 0 > tracing_on
* echo nop > current_tracer.
*/
if (!trace_osnoise_callback_enabled)
return;
trace_osnoise_callback_enabled = false;
/*
* Make sure that ftrace_nmi_enter/exit() see
* trace_osnoise_callback_enabled as false before continuing.
*/
barrier();
stop_per_cpu_kthreads();
osnoise_unhook_events();
}
static void osnoise_tracer_start(struct trace_array *tr)
{
int retval;
/*
* If the instance is already registered, there is no need to
* register it again.
*/
if (osnoise_instance_registered(tr))
return;
retval = osnoise_workload_start();
if (retval)
pr_err(BANNER "Error starting osnoise tracer\n");
osnoise_register_instance(tr);
}
static void osnoise_tracer_stop(struct trace_array *tr)
{
osnoise_unregister_instance(tr);
osnoise_workload_stop();
}
static int osnoise_tracer_init(struct trace_array *tr)
{
/*
* Only allow osnoise tracer if timerlat tracer is not running
* already.
*/
if (timerlat_enabled())
return -EBUSY;
tr->max_latency = 0;
osnoise_tracer_start(tr);
return 0;
}
static void osnoise_tracer_reset(struct trace_array *tr)
{
osnoise_tracer_stop(tr);
}
static struct tracer osnoise_tracer __read_mostly = {
.name = "osnoise",
.init = osnoise_tracer_init,
.reset = osnoise_tracer_reset,
.start = osnoise_tracer_start,
.stop = osnoise_tracer_stop,
.print_header = print_osnoise_headers,
.allow_instances = true,
};
#ifdef CONFIG_TIMERLAT_TRACER
static void timerlat_tracer_start(struct trace_array *tr)
{
int retval;
/*
* If the instance is already registered, there is no need to
* register it again.
*/
if (osnoise_instance_registered(tr))
return;
retval = osnoise_workload_start();
if (retval)
pr_err(BANNER "Error starting timerlat tracer\n");
osnoise_register_instance(tr);
return;
}
static void timerlat_tracer_stop(struct trace_array *tr)
{
int cpu;
osnoise_unregister_instance(tr);
/*
* Instruct the threads to stop only if this is the last instance.
*/
if (!osnoise_has_registered_instances()) {
for_each_online_cpu(cpu)
per_cpu(per_cpu_osnoise_var, cpu).sampling = 0;
}
osnoise_workload_stop();
}
static int timerlat_tracer_init(struct trace_array *tr)
{
/*
* Only allow timerlat tracer if osnoise tracer is not running already.
*/
if (osnoise_has_registered_instances() && !osnoise_data.timerlat_tracer)
return -EBUSY;
/*
* If this is the first instance, set timerlat_tracer to block
* osnoise tracer start.
*/
if (!osnoise_has_registered_instances())
osnoise_data.timerlat_tracer = 1;
tr->max_latency = 0;
timerlat_tracer_start(tr);
return 0;
}
static void timerlat_tracer_reset(struct trace_array *tr)
{
timerlat_tracer_stop(tr);
/*
* If this is the last instance, reset timerlat_tracer allowing
* osnoise to be started.
*/
if (!osnoise_has_registered_instances())
osnoise_data.timerlat_tracer = 0;
}
static struct tracer timerlat_tracer __read_mostly = {
.name = "timerlat",
.init = timerlat_tracer_init,
.reset = timerlat_tracer_reset,
.start = timerlat_tracer_start,
.stop = timerlat_tracer_stop,
.print_header = print_timerlat_headers,
.allow_instances = true,
};
__init static int init_timerlat_tracer(void)
{
return register_tracer(&timerlat_tracer);
}
#else /* CONFIG_TIMERLAT_TRACER */
__init static int init_timerlat_tracer(void)
{
return 0;
}
#endif /* CONFIG_TIMERLAT_TRACER */
__init static int init_osnoise_tracer(void)
{
int ret;
mutex_init(&interface_lock);
cpumask_copy(&osnoise_cpumask, cpu_all_mask);
ret = register_tracer(&osnoise_tracer);
if (ret) {
pr_err(BANNER "Error registering osnoise!\n");
return ret;
}
ret = init_timerlat_tracer();
if (ret) {
pr_err(BANNER "Error registering timerlat!\n");
return ret;
}
osnoise_init_hotplug_support();
INIT_LIST_HEAD_RCU(&osnoise_instances);
init_tracefs();
return 0;
}
late_initcall(init_osnoise_tracer);