Commit 3dd80953 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

tracing: Add trigger file for trace_markers tracefs/ftrace/print 



Allow writing to the trace_markers file initiate triggers defined in
tracefs/ftrace/print/trigger file. This will allow of user space to trigger
the same type of triggers (including histograms) that the trace events use.

Had to create a ftrace_event_register() function that will become the
trace_marker print event's reg() function. This is required because of how
triggers are enabled:

  event_trigger_write() {
    event_trigger_regex_write() {
      trigger_process_regex() {
        for p in trigger_commands {
          p->func(); /* trigger_snapshot_cmd->func */
            event_trigger_callback() {
              cmd_ops->reg() /* register_trigger() */ {
                trace_event_trigger_enable_disable() {
                  trace_event_enable_disable() {
                    call->class->reg();

Without the reg() function, the trigger code will call a NULL pointer and
crash the system.

Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Karim Yaghmour <karim.yaghmour@opersys.com>
Cc: Brendan Gregg <bgregg@netflix.com>
Suggested-by: default avatarJoel Fernandes <joelaf@google.com>
Reviewed-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 5d948c86

kernel/trace/trace.c

+17 −0
Original line number Diff line number Diff line
@@ -6074,6 +6074,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 
{

	struct trace_array *tr = filp->private_data;

	struct ring_buffer_event *event;

	enum event_trigger_type tt = ETT_NONE;

	struct ring_buffer *buffer;

	struct print_entry *entry;

	unsigned long irq_flags;
@@ -6122,6 +6123,12 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 
		written = cnt;

	len = cnt;



	if (tr->trace_marker_file && !list_empty(&tr->trace_marker_file->triggers)) {

		/* do not add \n before testing triggers, but add \0 */

		entry->buf[cnt] = '\0';

		tt = event_triggers_call(tr->trace_marker_file, entry, event);

	}



	if (entry->buf[cnt - 1] != '\n') {

		entry->buf[cnt] = '\n';

		entry->buf[cnt + 1] = '\0';
@@ -6130,6 +6137,9 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, 


	__buffer_unlock_commit(buffer, event);



	if (tt)

		event_triggers_post_call(tr->trace_marker_file, tt);



	if (written > 0)

		*fpos += written;
@@ -7896,6 +7906,7 @@ static __init void create_trace_instances(struct dentry *d_tracer) 
static void

init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)

{

	struct trace_event_file *file;

	int cpu;



	trace_create_file("available_tracers", 0444, d_tracer,
@@ -7928,6 +7939,12 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer) 
	trace_create_file("trace_marker", 0220, d_tracer,

			  tr, &tracing_mark_fops);



	file = __find_event_file(tr, "ftrace", "print");

	if (file && file->dir)

		trace_create_file("trigger", 0644, file->dir, file,

				  &event_trigger_fops);

	tr->trace_marker_file = file;



	trace_create_file("trace_marker_raw", 0220, d_tracer,

			  tr, &tracing_mark_raw_fops);

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -259,6 +259,7 @@ struct trace_array { 
	struct trace_options	*topts;

	struct list_head	systems;

	struct list_head	events;

	struct trace_event_file *trace_marker_file;

	cpumask_var_t		tracing_cpumask; /* only trace on set CPUs */

	int			ref;

#ifdef CONFIG_FUNCTION_TRACER

kernel/trace/trace_entries.h

+4 −2
Original line number Diff line number Diff line
@@ -230,7 +230,7 @@ FTRACE_ENTRY(bprint, bprint_entry, 
	FILTER_OTHER

);



FTRACE_ENTRY(print, print_entry,

FTRACE_ENTRY_REG(print, print_entry,



	TRACE_PRINT,
@@ -242,7 +242,9 @@ FTRACE_ENTRY(print, print_entry, 
	F_printk("%ps: %s",

		 (void *)__entry->ip, __entry->buf),



	FILTER_OTHER

	FILTER_OTHER,



	ftrace_event_register

);



FTRACE_ENTRY(raw_data, raw_data_entry,

kernel/trace/trace_export.c

+7 −0
Original line number Diff line number Diff line
@@ -14,6 +14,13 @@ 


#include "trace_output.h"



/* Stub function for events with triggers */

static int ftrace_event_register(struct trace_event_call *call,

				 enum trace_reg type, void *data)

{

	return 0;

}



#undef TRACE_SYSTEM

#define TRACE_SYSTEM	ftrace

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