trace_irqsoff.c

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/*
 * trace irqs off critical timings
 *
 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
 * Copyright (C) 2008 Ingo Molnar <[email protected]>
 *
 * From code in the latency_tracer, that is:
 *
 *  Copyright (C) 2004-2006 Ingo Molnar
 *  Copyright (C) 2004 William Lee Irwin III
 */
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/fs.h>

#include "trace.h"

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_lat_flag;

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(void)
{
    return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
}
#else
# define preempt_trace() (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

#define TRACE_DISPLAY_GRAPH 1

static struct tracer_opt trace_opts[] = {
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    /* display latency trace as call graph */
    { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
#endif
    { } /* Empty entry */
};

static struct tracer_flags tracer_flags = {
    .val  = 0,
    .opts = trace_opts,
};

#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)

/*
 * 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 */
    if (!irqs_disabled_flags(*flags))
        return 0;

    *data = tr->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);
}

static struct ftrace_ops trace_ops __read_mostly =
{
    .func = irqsoff_tracer_call,
    .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
};
#endif /* CONFIG_FUNCTION_TRACER */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
{
    int cpu;

    if (!(bit & TRACE_DISPLAY_GRAPH))
        return -EINVAL;

    if (!(is_graph() ^ set))
        return 0;

    stop_irqsoff_tracer(irqsoff_trace, !set);

    for_each_possible_cpu(cpu)
        per_cpu(tracing_cpu, cpu) = 0;

    tracing_max_latency = 0;
    tracing_reset_online_cpus(irqsoff_trace);

    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 (!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;

    if (!func_prolog_dec(tr, &data, &flags))
        return;

    pc = preempt_count();
    __trace_graph_return(tr, trace, flags, pc);
    atomic_dec(&data->disabled);
}

static void irqsoff_trace_open(struct trace_iterator *iter)
{
    if (is_graph())
        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_ABS_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())
        return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);

    return TRACE_TYPE_UNHANDLED;
}

static void irqsoff_print_header(struct seq_file *s)
{
    if (is_graph())
        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())
        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 int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
{
    return -EINVAL;
}

static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
{
    return -1;
}

static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
{
    return TRACE_TYPE_UNHANDLED;
}

static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
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 int report_latency(cycle_t delta)
{
    if (tracing_thresh) {
        if (delta < tracing_thresh)
            return 0;
    } else {
        if (delta <= tracing_max_latency)
            return 0;
    }
    return 1;
}

static void
check_critical_timing(struct trace_array *tr,
              struct trace_array_cpu *data,
              unsigned long parent_ip,
              int cpu)
{
    cycle_t 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(delta))
        goto out;

    raw_spin_lock_irqsave(&max_trace_lock, flags);

    /* check if we are still the max latency */
    if (!report_latency(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())) {
        tracing_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 inline void
start_critical_timing(unsigned long ip, unsigned long parent_ip)
{
    int cpu;
    struct trace_array *tr = irqsoff_trace;
    struct trace_array_cpu *data;
    unsigned long flags;

    if (likely(!tracer_enabled))
        return;

    cpu = raw_smp_processor_id();

    if (per_cpu(tracing_cpu, cpu))
        return;

    data = tr->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, preempt_count());

    per_cpu(tracing_cpu, cpu) = 1;

    atomic_dec(&data->disabled);
}

static inline void
stop_critical_timing(unsigned long ip, unsigned long parent_ip)
{
    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)
        return;

    data = tr->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, preempt_count());
    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)
{
    if (preempt_trace() || irq_trace())
        start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL_GPL(start_critical_timings);

void stop_critical_timings(void)
{
    if (preempt_trace() || irq_trace())
        stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL_GPL(stop_critical_timings);

#ifdef CONFIG_IRQSOFF_TRACER
#ifdef CONFIG_PROVE_LOCKING
void time_hardirqs_on(unsigned long a0, unsigned long a1)
{
    if (!preempt_trace() && irq_trace())
        stop_critical_timing(a0, a1);
}

void time_hardirqs_off(unsigned long a0, unsigned long a1)
{
    if (!preempt_trace() && irq_trace())
        start_critical_timing(a0, a1);
}

#else /* !CONFIG_PROVE_LOCKING */

/*
 * Stubs:
 */

void trace_softirqs_on(unsigned long ip)
{
}

void trace_softirqs_off(unsigned long ip)
{
}

inline void print_irqtrace_events(struct task_struct *curr)
{
}

/*
 * We are only interested in hardirq on/off events:
 */
void trace_hardirqs_on(void)
{
    if (!preempt_trace() && irq_trace())
        stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_on);

void trace_hardirqs_off(void)
{
    if (!preempt_trace() && irq_trace())
        start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
}
EXPORT_SYMBOL(trace_hardirqs_off);

void trace_hardirqs_on_caller(unsigned long caller_addr)
{
    if (!preempt_trace() && irq_trace())
        stop_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_on_caller);

void trace_hardirqs_off_caller(unsigned long caller_addr)
{
    if (!preempt_trace() && irq_trace())
        start_critical_timing(CALLER_ADDR0, caller_addr);
}
EXPORT_SYMBOL(trace_hardirqs_off_caller);

#endif /* CONFIG_PROVE_LOCKING */
#endif /*  CONFIG_IRQSOFF_TRACER */

#ifdef CONFIG_PREEMPT_TRACER
void trace_preempt_on(unsigned long a0, unsigned long a1)
{
    if (preempt_trace() && !irq_trace())
        stop_critical_timing(a0, a1);
}

void trace_preempt_off(unsigned long a0, unsigned long a1)
{
    if (preempt_trace() && !irq_trace())
        start_critical_timing(a0, a1);
}
#endif /* CONFIG_PREEMPT_TRACER */

static int start_irqsoff_tracer(struct trace_array *tr, int graph)
{
    int ret = 0;

    if (!graph)
        ret = register_ftrace_function(&trace_ops);
    else
        ret = register_ftrace_graph(&irqsoff_graph_return,
                        &irqsoff_graph_entry);

    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;

    if (!graph)
        unregister_ftrace_function(&trace_ops);
    else
        unregister_ftrace_graph();
}

static void __irqsoff_tracer_init(struct trace_array *tr)
{
    save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
    trace_flags |= TRACE_ITER_LATENCY_FMT;

    tracing_max_latency = 0;
    irqsoff_trace = tr;
    /* make sure that the tracer is visible */
    smp_wmb();
    tracing_reset_online_cpus(tr);

    if (start_irqsoff_tracer(tr, is_graph()))
        printk(KERN_ERR "failed to start irqsoff tracer\n");
}

static void irqsoff_tracer_reset(struct trace_array *tr)
{
    stop_irqsoff_tracer(tr, is_graph());

    if (!save_lat_flag)
        trace_flags &= ~TRACE_ITER_LATENCY_FMT;
}

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
static int irqsoff_tracer_init(struct trace_array *tr)
{
    trace_type = TRACER_IRQS_OFF;

    __irqsoff_tracer_init(tr);
    return 0;
}
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  = 1,
    .print_header   = irqsoff_print_header,
    .print_line     = irqsoff_print_line,
    .flags      = &tracer_flags,
    .set_flag   = irqsoff_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
    .selftest    = trace_selftest_startup_irqsoff,
#endif
    .open           = irqsoff_trace_open,
    .close          = irqsoff_trace_close,
    .use_max_tr = 1,
};
# define register_irqsoff(trace) register_tracer(&trace)
#else
# define register_irqsoff(trace) do { } while (0)
#endif

#ifdef CONFIG_PREEMPT_TRACER
static int preemptoff_tracer_init(struct trace_array *tr)
{
    trace_type = TRACER_PREEMPT_OFF;

    __irqsoff_tracer_init(tr);
    return 0;
}

static struct tracer preemptoff_tracer __read_mostly =
{
    .name       = "preemptoff",
    .init       = preemptoff_tracer_init,
    .reset      = irqsoff_tracer_reset,
    .start      = irqsoff_tracer_start,
    .stop       = irqsoff_tracer_stop,
    .print_max  = 1,
    .print_header   = irqsoff_print_header,
    .print_line     = irqsoff_print_line,
    .flags      = &tracer_flags,
    .set_flag   = irqsoff_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
    .selftest    = trace_selftest_startup_preemptoff,
#endif
    .open       = irqsoff_trace_open,
    .close      = irqsoff_trace_close,
    .use_max_tr = 1,
};
# define register_preemptoff(trace) register_tracer(&trace)
#else
# define register_preemptoff(trace) do { } while (0)
#endif

#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;

    __irqsoff_tracer_init(tr);
    return 0;
}

static struct tracer preemptirqsoff_tracer __read_mostly =
{
    .name       = "preemptirqsoff",
    .init       = preemptirqsoff_tracer_init,
    .reset      = irqsoff_tracer_reset,
    .start      = irqsoff_tracer_start,
    .stop       = irqsoff_tracer_stop,
    .print_max  = 1,
    .print_header   = irqsoff_print_header,
    .print_line     = irqsoff_print_line,
    .flags      = &tracer_flags,
    .set_flag   = irqsoff_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
    .selftest    = trace_selftest_startup_preemptirqsoff,
#endif
    .open       = irqsoff_trace_open,
    .close      = irqsoff_trace_close,
    .use_max_tr = 1,
};

# define register_preemptirqsoff(trace) register_tracer(&trace)
#else
# define register_preemptirqsoff(trace) do { } while (0)
#endif

__init static int init_irqsoff_tracer(void)
{
    register_irqsoff(irqsoff_tracer);
    register_preemptoff(preemptoff_tracer);
    register_preemptirqsoff(preemptirqsoff_tracer);

    return 0;
}
device_initcall(init_irqsoff_tracer);