![Steven Rostedt (Red Hat)](/assets/img/avatar_default.png)
Currently, the only way to stop the latency tracers from doing function tracing is to fully disable the function tracer from the proc file system: echo 0 > /proc/sys/kernel/ftrace_enabled This is a big hammer approach as it disables function tracing for all users. This includes kprobes, perf, stack tracer, etc. Instead, create a function-trace option that the latency tracers can check to determine if it should enable function tracing or not. This option can be set or cleared even while the tracer is active and the tracers will disable or enable function tracing depending on how the option was set. Instead of using the proc file, disable latency function tracing with echo 0 > /debug/tracing/options/function-trace Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Clark Williams <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
754 lines
17 KiB
C
754 lines
17 KiB
C
/*
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* trace irqs off critical timings
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
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*
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* From code in the latency_tracer, that is:
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*
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* Copyright (C) 2004-2006 Ingo Molnar
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* Copyright (C) 2004 Nadia Yvette Chambers
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*/
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#include <linux/kallsyms.h>
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#include <linux/debugfs.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/ftrace.h>
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#include <linux/fs.h>
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#include "trace.h"
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static struct trace_array *irqsoff_trace __read_mostly;
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static int tracer_enabled __read_mostly;
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static DEFINE_PER_CPU(int, tracing_cpu);
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static DEFINE_RAW_SPINLOCK(max_trace_lock);
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enum {
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TRACER_IRQS_OFF = (1 << 1),
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TRACER_PREEMPT_OFF = (1 << 2),
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};
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static int trace_type __read_mostly;
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static int save_flags;
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static bool function_enabled;
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static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
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static int start_irqsoff_tracer(struct trace_array *tr, int graph);
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#ifdef CONFIG_PREEMPT_TRACER
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static inline int
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preempt_trace(void)
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{
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return ((trace_type & TRACER_PREEMPT_OFF) && preempt_count());
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}
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#else
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# define preempt_trace() (0)
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#endif
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#ifdef CONFIG_IRQSOFF_TRACER
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static inline int
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irq_trace(void)
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{
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return ((trace_type & TRACER_IRQS_OFF) &&
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irqs_disabled());
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}
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#else
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# define irq_trace() (0)
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#endif
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#define TRACE_DISPLAY_GRAPH 1
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static struct tracer_opt trace_opts[] = {
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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/* display latency trace as call graph */
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{ TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
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#endif
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{ } /* Empty entry */
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};
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static struct tracer_flags tracer_flags = {
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.val = 0,
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.opts = trace_opts,
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};
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#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
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/*
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* Sequence count - we record it when starting a measurement and
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* skip the latency if the sequence has changed - some other section
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* did a maximum and could disturb our measurement with serial console
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* printouts, etc. Truly coinciding maximum latencies should be rare
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* and what happens together happens separately as well, so this doesn't
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* decrease the validity of the maximum found:
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*/
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static __cacheline_aligned_in_smp unsigned long max_sequence;
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#ifdef CONFIG_FUNCTION_TRACER
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/*
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* Prologue for the preempt and irqs off function tracers.
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*
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* Returns 1 if it is OK to continue, and data->disabled is
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* incremented.
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* 0 if the trace is to be ignored, and data->disabled
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* is kept the same.
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*
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* Note, this function is also used outside this ifdef but
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* inside the #ifdef of the function graph tracer below.
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* This is OK, since the function graph tracer is
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* dependent on the function tracer.
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*/
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static int func_prolog_dec(struct trace_array *tr,
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struct trace_array_cpu **data,
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unsigned long *flags)
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{
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long disabled;
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int cpu;
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/*
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* Does not matter if we preempt. We test the flags
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* afterward, to see if irqs are disabled or not.
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* If we preempt and get a false positive, the flags
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* test will fail.
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*/
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cpu = raw_smp_processor_id();
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if (likely(!per_cpu(tracing_cpu, cpu)))
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return 0;
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local_save_flags(*flags);
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/* slight chance to get a false positive on tracing_cpu */
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if (!irqs_disabled_flags(*flags))
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return 0;
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*data = per_cpu_ptr(tr->trace_buffer.data, cpu);
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disabled = atomic_inc_return(&(*data)->disabled);
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if (likely(disabled == 1))
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return 1;
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atomic_dec(&(*data)->disabled);
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return 0;
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}
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/*
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* irqsoff uses its own tracer function to keep the overhead down:
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*/
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static void
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irqsoff_tracer_call(unsigned long ip, unsigned long parent_ip,
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struct ftrace_ops *op, struct pt_regs *pt_regs)
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{
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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if (!func_prolog_dec(tr, &data, &flags))
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return;
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trace_function(tr, ip, parent_ip, flags, preempt_count());
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atomic_dec(&data->disabled);
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}
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static struct ftrace_ops trace_ops __read_mostly =
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{
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.func = irqsoff_tracer_call,
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.flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
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};
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#endif /* CONFIG_FUNCTION_TRACER */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
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{
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int cpu;
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if (!(bit & TRACE_DISPLAY_GRAPH))
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return -EINVAL;
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if (!(is_graph() ^ set))
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return 0;
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stop_irqsoff_tracer(irqsoff_trace, !set);
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for_each_possible_cpu(cpu)
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per_cpu(tracing_cpu, cpu) = 0;
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tracing_max_latency = 0;
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tracing_reset_online_cpus(&irqsoff_trace->trace_buffer);
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return start_irqsoff_tracer(irqsoff_trace, set);
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}
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static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
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{
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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int ret;
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int pc;
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if (!func_prolog_dec(tr, &data, &flags))
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return 0;
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pc = preempt_count();
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ret = __trace_graph_entry(tr, trace, flags, pc);
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atomic_dec(&data->disabled);
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return ret;
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}
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static void irqsoff_graph_return(struct ftrace_graph_ret *trace)
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{
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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int pc;
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if (!func_prolog_dec(tr, &data, &flags))
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return;
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pc = preempt_count();
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__trace_graph_return(tr, trace, flags, pc);
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atomic_dec(&data->disabled);
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}
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static void irqsoff_trace_open(struct trace_iterator *iter)
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{
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if (is_graph())
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graph_trace_open(iter);
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}
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static void irqsoff_trace_close(struct trace_iterator *iter)
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{
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if (iter->private)
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graph_trace_close(iter);
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}
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#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_CPU | \
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TRACE_GRAPH_PRINT_PROC | \
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TRACE_GRAPH_PRINT_ABS_TIME | \
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TRACE_GRAPH_PRINT_DURATION)
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static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
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{
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/*
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* In graph mode call the graph tracer output function,
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* otherwise go with the TRACE_FN event handler
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*/
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if (is_graph())
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return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
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return TRACE_TYPE_UNHANDLED;
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}
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static void irqsoff_print_header(struct seq_file *s)
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{
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if (is_graph())
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print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
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else
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trace_default_header(s);
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}
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static void
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__trace_function(struct trace_array *tr,
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unsigned long ip, unsigned long parent_ip,
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unsigned long flags, int pc)
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{
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if (is_graph())
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trace_graph_function(tr, ip, parent_ip, flags, pc);
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else
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trace_function(tr, ip, parent_ip, flags, pc);
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}
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#else
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#define __trace_function trace_function
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static int irqsoff_set_flag(u32 old_flags, u32 bit, int set)
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{
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return -EINVAL;
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}
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static int irqsoff_graph_entry(struct ftrace_graph_ent *trace)
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{
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return -1;
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}
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static enum print_line_t irqsoff_print_line(struct trace_iterator *iter)
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{
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return TRACE_TYPE_UNHANDLED;
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}
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static void irqsoff_graph_return(struct ftrace_graph_ret *trace) { }
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static void irqsoff_trace_open(struct trace_iterator *iter) { }
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static void irqsoff_trace_close(struct trace_iterator *iter) { }
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#ifdef CONFIG_FUNCTION_TRACER
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static void irqsoff_print_header(struct seq_file *s)
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{
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trace_default_header(s);
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}
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#else
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static void irqsoff_print_header(struct seq_file *s)
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{
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trace_latency_header(s);
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}
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#endif /* CONFIG_FUNCTION_TRACER */
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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/*
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* Should this new latency be reported/recorded?
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*/
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static int report_latency(cycle_t delta)
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{
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if (tracing_thresh) {
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if (delta < tracing_thresh)
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return 0;
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} else {
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if (delta <= tracing_max_latency)
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return 0;
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}
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return 1;
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}
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static void
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check_critical_timing(struct trace_array *tr,
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struct trace_array_cpu *data,
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unsigned long parent_ip,
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int cpu)
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{
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cycle_t T0, T1, delta;
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unsigned long flags;
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int pc;
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T0 = data->preempt_timestamp;
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T1 = ftrace_now(cpu);
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delta = T1-T0;
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local_save_flags(flags);
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pc = preempt_count();
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if (!report_latency(delta))
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goto out;
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raw_spin_lock_irqsave(&max_trace_lock, flags);
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/* check if we are still the max latency */
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if (!report_latency(delta))
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goto out_unlock;
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__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
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/* Skip 5 functions to get to the irq/preempt enable function */
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__trace_stack(tr, flags, 5, pc);
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if (data->critical_sequence != max_sequence)
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goto out_unlock;
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data->critical_end = parent_ip;
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if (likely(!is_tracing_stopped())) {
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tracing_max_latency = delta;
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update_max_tr_single(tr, current, cpu);
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}
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max_sequence++;
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out_unlock:
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raw_spin_unlock_irqrestore(&max_trace_lock, flags);
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out:
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data->critical_sequence = max_sequence;
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data->preempt_timestamp = ftrace_now(cpu);
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__trace_function(tr, CALLER_ADDR0, parent_ip, flags, pc);
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}
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static inline void
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start_critical_timing(unsigned long ip, unsigned long parent_ip)
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{
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int cpu;
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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if (likely(!tracer_enabled))
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return;
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cpu = raw_smp_processor_id();
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if (per_cpu(tracing_cpu, cpu))
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return;
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data = per_cpu_ptr(tr->trace_buffer.data, cpu);
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if (unlikely(!data) || atomic_read(&data->disabled))
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return;
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atomic_inc(&data->disabled);
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data->critical_sequence = max_sequence;
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data->preempt_timestamp = ftrace_now(cpu);
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data->critical_start = parent_ip ? : ip;
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local_save_flags(flags);
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__trace_function(tr, ip, parent_ip, flags, preempt_count());
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per_cpu(tracing_cpu, cpu) = 1;
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atomic_dec(&data->disabled);
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}
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static inline void
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stop_critical_timing(unsigned long ip, unsigned long parent_ip)
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{
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int cpu;
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struct trace_array *tr = irqsoff_trace;
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struct trace_array_cpu *data;
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unsigned long flags;
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cpu = raw_smp_processor_id();
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/* Always clear the tracing cpu on stopping the trace */
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if (unlikely(per_cpu(tracing_cpu, cpu)))
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per_cpu(tracing_cpu, cpu) = 0;
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else
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return;
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if (!tracer_enabled)
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return;
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data = per_cpu_ptr(tr->trace_buffer.data, cpu);
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if (unlikely(!data) ||
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!data->critical_start || atomic_read(&data->disabled))
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return;
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atomic_inc(&data->disabled);
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local_save_flags(flags);
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__trace_function(tr, ip, parent_ip, flags, preempt_count());
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check_critical_timing(tr, data, parent_ip ? : ip, cpu);
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data->critical_start = 0;
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atomic_dec(&data->disabled);
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}
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/* start and stop critical timings used to for stoppage (in idle) */
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void start_critical_timings(void)
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{
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if (preempt_trace() || irq_trace())
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start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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EXPORT_SYMBOL_GPL(start_critical_timings);
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void stop_critical_timings(void)
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{
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if (preempt_trace() || irq_trace())
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stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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EXPORT_SYMBOL_GPL(stop_critical_timings);
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#ifdef CONFIG_IRQSOFF_TRACER
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#ifdef CONFIG_PROVE_LOCKING
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void time_hardirqs_on(unsigned long a0, unsigned long a1)
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{
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if (!preempt_trace() && irq_trace())
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stop_critical_timing(a0, a1);
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}
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void time_hardirqs_off(unsigned long a0, unsigned long a1)
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{
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if (!preempt_trace() && irq_trace())
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start_critical_timing(a0, a1);
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}
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#else /* !CONFIG_PROVE_LOCKING */
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/*
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* Stubs:
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*/
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void trace_softirqs_on(unsigned long ip)
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{
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}
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void trace_softirqs_off(unsigned long ip)
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{
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}
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inline void print_irqtrace_events(struct task_struct *curr)
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{
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}
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/*
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* We are only interested in hardirq on/off events:
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*/
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void trace_hardirqs_on(void)
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{
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if (!preempt_trace() && irq_trace())
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stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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EXPORT_SYMBOL(trace_hardirqs_on);
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void trace_hardirqs_off(void)
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{
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if (!preempt_trace() && irq_trace())
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start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
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}
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EXPORT_SYMBOL(trace_hardirqs_off);
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void trace_hardirqs_on_caller(unsigned long caller_addr)
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{
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if (!preempt_trace() && irq_trace())
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stop_critical_timing(CALLER_ADDR0, caller_addr);
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}
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EXPORT_SYMBOL(trace_hardirqs_on_caller);
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void trace_hardirqs_off_caller(unsigned long caller_addr)
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{
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if (!preempt_trace() && irq_trace())
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start_critical_timing(CALLER_ADDR0, caller_addr);
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}
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EXPORT_SYMBOL(trace_hardirqs_off_caller);
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#endif /* CONFIG_PROVE_LOCKING */
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#endif /* CONFIG_IRQSOFF_TRACER */
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#ifdef CONFIG_PREEMPT_TRACER
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void trace_preempt_on(unsigned long a0, unsigned long a1)
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{
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if (preempt_trace() && !irq_trace())
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stop_critical_timing(a0, a1);
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}
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void trace_preempt_off(unsigned long a0, unsigned long a1)
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{
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if (preempt_trace() && !irq_trace())
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start_critical_timing(a0, a1);
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}
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#endif /* CONFIG_PREEMPT_TRACER */
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static int register_irqsoff_function(int graph, int set)
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{
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int ret;
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/* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
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if (function_enabled || (!set && !(trace_flags & TRACE_ITER_FUNCTION)))
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return 0;
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if (graph)
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ret = register_ftrace_graph(&irqsoff_graph_return,
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&irqsoff_graph_entry);
|
|
else
|
|
ret = register_ftrace_function(&trace_ops);
|
|
|
|
if (!ret)
|
|
function_enabled = true;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static void unregister_irqsoff_function(int graph)
|
|
{
|
|
if (!function_enabled)
|
|
return;
|
|
|
|
if (graph)
|
|
unregister_ftrace_graph();
|
|
else
|
|
unregister_ftrace_function(&trace_ops);
|
|
|
|
function_enabled = false;
|
|
}
|
|
|
|
static void irqsoff_function_set(int set)
|
|
{
|
|
if (set)
|
|
register_irqsoff_function(is_graph(), 1);
|
|
else
|
|
unregister_irqsoff_function(is_graph());
|
|
}
|
|
|
|
static int irqsoff_flag_changed(struct tracer *tracer, u32 mask, int set)
|
|
{
|
|
if (mask & TRACE_ITER_FUNCTION)
|
|
irqsoff_function_set(set);
|
|
|
|
return trace_keep_overwrite(tracer, mask, set);
|
|
}
|
|
|
|
static int start_irqsoff_tracer(struct trace_array *tr, int graph)
|
|
{
|
|
int ret;
|
|
|
|
ret = register_irqsoff_function(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(graph);
|
|
}
|
|
|
|
static void __irqsoff_tracer_init(struct trace_array *tr)
|
|
{
|
|
save_flags = 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);
|
|
|
|
tracing_max_latency = 0;
|
|
irqsoff_trace = tr;
|
|
/* make sure that the tracer is visible */
|
|
smp_wmb();
|
|
tracing_reset_online_cpus(&tr->trace_buffer);
|
|
|
|
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)
|
|
{
|
|
int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
|
|
int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
|
|
|
|
stop_irqsoff_tracer(tr, is_graph());
|
|
|
|
set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag);
|
|
set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag);
|
|
}
|
|
|
|
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 = true,
|
|
.print_header = irqsoff_print_header,
|
|
.print_line = irqsoff_print_line,
|
|
.flags = &tracer_flags,
|
|
.set_flag = irqsoff_set_flag,
|
|
.flag_changed = irqsoff_flag_changed,
|
|
#ifdef CONFIG_FTRACE_SELFTEST
|
|
.selftest = trace_selftest_startup_irqsoff,
|
|
#endif
|
|
.open = irqsoff_trace_open,
|
|
.close = irqsoff_trace_close,
|
|
.use_max_tr = true,
|
|
};
|
|
# 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 = true,
|
|
.print_header = irqsoff_print_header,
|
|
.print_line = irqsoff_print_line,
|
|
.flags = &tracer_flags,
|
|
.set_flag = irqsoff_set_flag,
|
|
.flag_changed = irqsoff_flag_changed,
|
|
#ifdef CONFIG_FTRACE_SELFTEST
|
|
.selftest = trace_selftest_startup_preemptoff,
|
|
#endif
|
|
.open = irqsoff_trace_open,
|
|
.close = irqsoff_trace_close,
|
|
.use_max_tr = true,
|
|
};
|
|
# 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 = true,
|
|
.print_header = irqsoff_print_header,
|
|
.print_line = irqsoff_print_line,
|
|
.flags = &tracer_flags,
|
|
.set_flag = irqsoff_set_flag,
|
|
.flag_changed = irqsoff_flag_changed,
|
|
#ifdef CONFIG_FTRACE_SELFTEST
|
|
.selftest = trace_selftest_startup_preemptirqsoff,
|
|
#endif
|
|
.open = irqsoff_trace_open,
|
|
.close = irqsoff_trace_close,
|
|
.use_max_tr = true,
|
|
};
|
|
|
|
# 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;
|
|
}
|
|
core_initcall(init_irqsoff_tracer);
|