trace_irqsoff.c
// SPDX-License-Identifier: GPL-2.0
/*
* trace irqs off critical timings
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
*
* From code in the latency_tracer, that is:
*
* Copyright (C) 2004-2006 Ingo Molnar
* Copyright (C) 2004 Nadia Yvette Chambers
*/
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/kprobes.h>
#include "trace.h"
#include <trace/events/preemptirq.h>
#if defined(CONFIG_IRQSOFF_TRACER) || defined(CONFIG_PREEMPT_TRACER)
static struct trace_array *irqsoff_trace __read_mostly;
static int tracer_enabled __read_mostly;
static DEFINE_PER_CPU(int, tracing_cpu);
static DEFINE_RAW_SPINLOCK(max_trace_lock);
enum {
TRACER_IRQS_OFF = (1 << 1),
TRACER_PREEMPT_OFF = (1 << 2),
};
static int trace_type __read_mostly;
static int save_flags;
static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
static int start_irqsoff_tracer(struct trace_array *tr, int graph);
#ifdef CONFIG_PREEMPT_TRACER
static inline int
preempt_trace(int pc)
{
return ((trace_type & TRACER_PREEMPT_OFF) && pc);
}
#else
# define preempt_trace(pc) (0)
#endif
#ifdef CONFIG_IRQSOFF_TRACER
static inline int
irq_trace(void)
{
return ((trace_type & TRACER_IRQS_OFF) &&
irqs_disabled());
}
#else
# define irq_trace() (0)
#endif
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int irqsoff_display_graph(struct trace_array *tr, int set);
# define is_graph(tr) ((tr)->trace_flags & TRACE_ITER_DISPLAY_GRAPH)
#else
static inline int irqsoff_display_graph(struct trace_array *tr, int set)
{
return -EINVAL;
}
# define is_graph(tr) false
#endif
/*
* Sequence count - we record it when starting a measurement and
* skip the latency if the sequence has changed - some other section
* did a maximum and could disturb our measurement with serial console
* printouts, etc. Truly coinciding maximum latencies should be rare
* and what happens together happens separately as well, so this doesn't
* decrease the validity of the maximum found:
*/
static __cacheline_aligned_in_smp unsigned long max_sequence;
#ifdef CONFIG_FUNCTION_TRACER
/*
* Prologue for the preempt and irqs off function tracers.
*
* Returns 1 if it is OK to continue, and data->disabled is
* incremented.
* 0 if the trace is to be ignored, and data->disabled
* is kept the same.
*
* Note, this function is also used outside this ifdef but
* inside the #ifdef of the function graph tracer below.
* This is OK, since the function graph tracer is
* dependent on the function tracer.
*/
static int func_prolog_dec(struct trace_array *tr,
struct trace_array_cpu **data,
unsigned long *flags)
{
long disabled;
int cpu;
/*
* Does not matter if we preempt. We test the flags
* afterward, to see if irqs are disabled or not.
* If we preempt and get a false positive, the flags
* test will fail.
*/
cpu = raw_smp_processor_id();
if (likely(!per_cpu(tracing_cpu, cpu)))
return 0;
local_save_flags(*flags);
/*
* Slight chance to get a false positive on tracing_cpu,
* although I'm starting to think there isn't a chance.
* Leave this for now just to be paranoid.
*/
if (!irqs_disabled_flags(*flags) && !preempt_count())
return 0;
*data = per_cpu_ptr(tr->array_buffer.data, cpu);
disabled = atomic_inc_return(&(*data)->disabled);
if (likely(disabled == 1))
return 1;
atomic_dec(&(*data)->disabled);
return 0;
}
/*
* irqsoff uses its own tracer function to keep the overhead down:
*/
static void
irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *pt_regs)
{
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
unsigned long flags;
if (!func_prolog_dec(tr, &data, &flags))
return;
trace_function(tr, ip, parent_ip, flags, preempt_count());
atomic_dec(&data->disabled);
}
#endif /* CONFIG_FUNCTION_TRACER */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int irqsoff_display_graph(struct trace_array *tr, int set)
{
int cpu;
if (!(is_graph(tr) ^ set))
return 0;
stop_irqsoff_tracer(irqsoff_trace, !set);
for_each_possible_cpu(cpu)
per_cpu(tracing_cpu, cpu) = 0;
tr->max_latency = 0;
tracing_reset_online_cpus(&irqsoff_trace->array_buffer);
return start_irqsoff_tracer(irqsoff_trace, set);
}
static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
{
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
unsigned long flags;
int ret;
int pc;
if (ftrace_graph_ignore_func(trace))
return 0;
/*
* Do not trace a function if it's filtered by set_graph_notrace.
* Make the index of ret stack negative to indicate that it should
* ignore further functions. But it needs its own ret stack entry
* to recover the original index in order to continue tracing after
* returning from the function.
*/
if (ftrace_graph_notrace_addr(trace->func))
return 1;
if (!func_prolog_dec(tr, &data, &flags))
return 0;
pc = preempt_count();
ret = __trace_graph_entry(tr, trace, flags, pc);
atomic_dec(&data->disabled);
return ret;
}
static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
{
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
unsigned long flags;
int pc;
ftrace_graph_addr_finish(trace);
if (!func_prolog_dec(tr, &data, &flags))
return;
pc = preempt_count();
__trace_graph_return(tr, trace, flags, pc);
atomic_dec(&data->disabled);
}
static struct fgraph_ops fgraph_ops = {
.entryfunc = &irqsoff_graph_entry,
.retfunc = &irqsoff_graph_return,
};
static void irqsoff_trace_open(struct trace_iterator *iter)
{
if (is_graph(iter->tr))
graph_trace_open(iter);
}
static void irqsoff_trace_close(struct trace_iterator *iter)
{
if (iter->private)
graph_trace_close(iter);
}
#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
TRACE_GRAPH_PRINT_PROC | \
TRACE_GRAPH_PRINT_REL_TIME | \
TRACE_GRAPH_PRINT_DURATION)
static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
{
/*
* In graph mode call the graph tracer output function,
* otherwise go with the TRACE_FN event handler
*/
if (is_graph(iter->tr))
return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
return TRACE_TYPE_UNHANDLED;
}
static void irqsoff_print_header(struct seq_file *s)
{
struct trace_array *tr = irqsoff_trace;
if (is_graph(tr))
print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
else
trace_default_header(s);
}
static void
__trace_function(struct trace_array *tr,
unsigned long ip, unsigned long parent_ip,
unsigned long flags, int pc)
{
if (is_graph(tr))
trace_graph_function(tr, ip, parent_ip, flags, pc);
else
trace_function(tr, ip, parent_ip, flags, pc);
}
#else
#define __trace_function trace_function
static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
{
return TRACE_TYPE_UNHANDLED;
}
static void irqsoff_trace_open(struct trace_iterator *iter) { }
static void irqsoff_trace_close(struct trace_iterator *iter) { }
#ifdef CONFIG_FUNCTION_TRACER
static void irqsoff_print_header(struct seq_file *s)
{
trace_default_header(s);
}
#else
static void irqsoff_print_header(struct seq_file *s)
{
trace_latency_header(s);
}
#endif /* CONFIG_FUNCTION_TRACER */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
/*
* Should this new latency be reported/recorded?
*/
static bool report_latency(struct trace_array *tr, u64 delta)
{
if (tracing_thresh) {
if (delta < tracing_thresh)
return false;
} else {
if (delta <= tr->max_latency)
return false;
}
return true;
}
static void
check_critical_timing(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long parent_ip,
int cpu)
{
u64 T0, T1, delta;
unsigned long flags;
int pc;
T0 = data->preempt_timestamp;
T1 = ftrace_now(cpu);
delta = T1-T0;
local_save_flags(flags);
pc = preempt_count();
if (!report_latency(tr, delta))
goto out;
raw_spin_lock_irqsave(&max_trace_lock, flags);
/* check if we are still the max latency */
if (!report_latency(tr, delta))
goto out_unlock;
__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
/* Skip 5 functions to get to the irq/preempt enable function */
__trace_stack(tr, flags, 5, pc);
if (data->critical_sequence != max_sequence)
goto out_unlock;
data->critical_end = parent_ip;
if (likely(!is_tracing_stopped())) {
tr->max_latency = delta;
update_max_tr_single(tr, current, cpu);
}
max_sequence++;
out_unlock:
raw_spin_unlock_irqrestore(&max_trace_lock, flags);
out:
data->critical_sequence = max_sequence;
data->preempt_timestamp = ftrace_now(cpu);
__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
}
static nokprobe_inline void
start_critical_timing(unsigned long ip, unsigned long parent_ip, int pc)
{
int cpu;
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
unsigned long flags;
if (!tracer_enabled || !tracing_is_enabled())
return;
cpu = raw_smp_processor_id();
if (per_cpu(tracing_cpu, cpu))
return;
data = per_cpu_ptr(tr->array_buffer.data, cpu);
if (unlikely(!data) || atomic_read(&data->disabled))
return;
atomic_inc(&data->disabled);
data->critical_sequence = max_sequence;
data->preempt_timestamp = ftrace_now(cpu);
data->critical_start = parent_ip ? : ip;
local_save_flags(flags);
__trace_function(tr, ip, parent_ip, flags, pc);
per_cpu(tracing_cpu, cpu) = 1;
atomic_dec(&data->disabled);
}
static nokprobe_inline void
stop_critical_timing(unsigned long ip, unsigned long parent_ip, int pc)
{
int cpu;
struct trace_array *tr = irqsoff_trace;
struct trace_array_cpu *data;
unsigned long flags;
cpu = raw_smp_processor_id();
/* Always clear the tracing cpu on stopping the trace */
if (unlikely(per_cpu(tracing_cpu, cpu)))
per_cpu(tracing_cpu, cpu) = 0;
else
return;
if (!tracer_enabled || !tracing_is_enabled())
return;
data = per_cpu_ptr(tr->array_buffer.data, cpu);
if (unlikely(!data) ||
!data->critical_start || atomic_read(&data->disabled))
return;
atomic_inc(&data->disabled);
local_save_flags(flags);
__trace_function(tr, ip, parent_ip, flags, pc);
check_critical_timing(tr, data, parent_ip ? : ip, cpu);
data->critical_start = 0;
atomic_dec(&data->disabled);
}
/* start and stop critical timings used to for stoppage (in idle) */
void start_critical_timings(void)
{
int pc = preempt_count();
if (preempt_trace(pc) || irq_trace())
start_critical_timing(CALLER_ADDR0, CALLER_ADDR1, pc);
}
EXPORT_SYMBOL_GPL(start_critical_timings);
NOKPROBE_SYMBOL(start_critical_timings);
void stop_critical_timings(void)
{
int pc = preempt_count();
if (preempt_trace(pc) || irq_trace())
stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1, pc);
}
EXPORT_SYMBOL_GPL(stop_critical_timings);
NOKPROBE_SYMBOL(stop_critical_timings);
#ifdef CONFIG_FUNCTION_TRACER
static bool function_enabled;
static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
{
int ret;
/* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
if (function_enabled || (!set && !(tr->trace_flags & TRACE_ITER_FUNCTION)))
return 0;
if (graph)
ret = register_ftrace_graph(&fgraph_ops);
else
ret = register_ftrace_function(tr->ops);
if (!ret)
function_enabled = true;
return ret;
}
static void unregister_irqsoff_function(struct trace_array *tr, int graph)
{
if (!function_enabled)
return;
if (graph)
unregister_ftrace_graph(&fgraph_ops);
else
unregister_ftrace_function(tr->ops);
function_enabled = false;
}
static int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
{
if (!(mask & TRACE_ITER_FUNCTION))
return 0;
if (set)
register_irqsoff_function(tr, is_graph(tr), 1);
else
unregister_irqsoff_function(tr, is_graph(tr));
return 1;
}
#else
static int register_irqsoff_function(struct trace_array *tr, int graph, int set)
{
return 0;
}
static void unregister_irqsoff_function(struct trace_array *tr, int graph) { }
static inline int irqsoff_function_set(struct trace_array *tr, u32 mask, int set)
{
return 0;
}
#endif /* CONFIG_FUNCTION_TRACER */
static int irqsoff_flag_changed(struct trace_array *tr, u32 mask, int set)
{
struct tracer *tracer = tr->current_trace;
if (irqsoff_function_set(tr, mask, set))
return 0;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
if (mask & TRACE_ITER_DISPLAY_GRAPH)
return irqsoff_display_graph(tr, set);
#endif
return trace_keep_overwrite(tracer, mask, set);
}
static int start_irqsoff_tracer(struct trace_array *tr, int graph)
{
int ret;
ret = register_irqsoff_function(tr, graph, 0);
if (!ret && tracing_is_enabled())
tracer_enabled = 1;
else
tracer_enabled = 0;
return ret;
}
static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
{
tracer_enabled = 0;
unregister_irqsoff_function(tr, graph);
}
static bool irqsoff_busy;
static int __irqsoff_tracer_init(struct trace_array *tr)
{
if (irqsoff_busy)
return -EBUSY;
save_flags = tr->trace_flags;
/* non overwrite screws up the latency tracers */
set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1);
set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1);
tr->max_latency = 0;
irqsoff_trace = tr;
/* make sure that the tracer is visible */
smp_wmb();
ftrace_init_array_ops(tr, irqsoff_tracer_call);
/* Only toplevel instance supports graph tracing */
if (start_irqsoff_tracer(tr, (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
is_graph(tr))))
printk(KERN_ERR "failed to start irqsoff tracer\n");
irqsoff_busy = true;
return 0;
}
static void __irqsoff_tracer_reset(struct trace_array *tr)
{
int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
stop_irqsoff_tracer(tr, is_graph(tr));
set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
ftrace_reset_array_ops(tr);
irqsoff_busy = false;
}
static void irqsoff_tracer_start(struct trace_array *tr)
{
tracer_enabled = 1;
}
static void irqsoff_tracer_stop(struct trace_array *tr)
{
tracer_enabled = 0;
}
#ifdef CONFIG_IRQSOFF_TRACER
/*
* We are only interested in hardirq on/off events:
*/
void tracer_hardirqs_on(unsigned long a0, unsigned long a1)
{
unsigned int pc = preempt_count();
if (!preempt_trace(pc) && irq_trace())
stop_critical_timing(a0, a1, pc);
}
NOKPROBE_SYMBOL(tracer_hardirqs_on);
void tracer_hardirqs_off(unsigned long a0, unsigned long a1)
{
unsigned int pc = preempt_count();
if (!preempt_trace(pc) && irq_trace())
start_critical_timing(a0, a1, pc);
}
NOKPROBE_SYMBOL(tracer_hardirqs_off);
static int irqsoff_tracer_init(struct trace_array *tr)
{
trace_type = TRACER_IRQS_OFF;
return __irqsoff_tracer_init(tr);
}
static void irqsoff_tracer_reset(struct trace_array *tr)
{
__irqsoff_tracer_reset(tr);
}
static struct tracer irqsoff_tracer __read_mostly =
{
.name = "irqsoff",
.init = irqsoff_tracer_init,
.reset = irqsoff_tracer_reset,
.start = irqsoff_tracer_start,
.stop = irqsoff_tracer_stop,
.print_max = true,
.print_header = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flag_changed = irqsoff_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_irqsoff,
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
.allow_instances = true,
.use_max_tr = true,
};
#endif /* CONFIG_IRQSOFF_TRACER */
#ifdef CONFIG_PREEMPT_TRACER
void tracer_preempt_on(unsigned long a0, unsigned long a1)
{
int pc = preempt_count();
if (preempt_trace(pc) && !irq_trace())
stop_critical_timing(a0, a1, pc);
}
void tracer_preempt_off(unsigned long a0, unsigned long a1)
{
int pc = preempt_count();
if (preempt_trace(pc) && !irq_trace())
start_critical_timing(a0, a1, pc);
}
static int preemptoff_tracer_init(struct trace_array *tr)
{
trace_type = TRACER_PREEMPT_OFF;
return __irqsoff_tracer_init(tr);
}
static void preemptoff_tracer_reset(struct trace_array *tr)
{
__irqsoff_tracer_reset(tr);
}
static struct tracer preemptoff_tracer __read_mostly =
{
.name = "preemptoff",
.init = preemptoff_tracer_init,
.reset = preemptoff_tracer_reset,
.start = irqsoff_tracer_start,
.stop = irqsoff_tracer_stop,
.print_max = true,
.print_header = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flag_changed = irqsoff_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_preemptoff,
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
.allow_instances = true,
.use_max_tr = true,
};
#endif /* CONFIG_PREEMPT_TRACER */
#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
static int preemptirqsoff_tracer_init(struct trace_array *tr)
{
trace_type = TRACER_IRQS_OFF | TRACER_PREEMPT_OFF;
return __irqsoff_tracer_init(tr);
}
static void preemptirqsoff_tracer_reset(struct trace_array *tr)
{
__irqsoff_tracer_reset(tr);
}
static struct tracer preemptirqsoff_tracer __read_mostly =
{
.name = "preemptirqsoff",
.init = preemptirqsoff_tracer_init,
.reset = preemptirqsoff_tracer_reset,
.start = irqsoff_tracer_start,
.stop = irqsoff_tracer_stop,
.print_max = true,
.print_header = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flag_changed = irqsoff_flag_changed,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_preemptirqsoff,
#endif
.open = irqsoff_trace_open,
.close = irqsoff_trace_close,
.allow_instances = true,
.use_max_tr = true,
};
#endif
__init static int init_irqsoff_tracer(void)
{
#ifdef CONFIG_IRQSOFF_TRACER
register_tracer(&irqsoff_tracer);
#endif
#ifdef CONFIG_PREEMPT_TRACER
register_tracer(&preemptoff_tracer);
#endif
#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
register_tracer(&preemptirqsoff_tracer);
#endif
return 0;
}
core_initcall(init_irqsoff_tracer);
#endif /* IRQSOFF_TRACER || PREEMPTOFF_TRACER */