ftrace: Add task_comm support for trace_event (b11c53e1) · Commits · e / devices / android_kernel_sony_msm8994_rework

If we enable a trace event alone without any tracer running (such as function tracer, sched switch tracer, etc...) it can't output enough task command information. We need to use the tracing_{start/stop}_cmdline_record() helpers which are designed to keep track of cmdlines for any tasks that were scheduled during the tracing. Before this patch: # echo 1 > debugfs/tracing/events/sched/sched_switch/enable # cat debugfs/tracing/trace # tracer: nop # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | <...>-2289 [000] 526276.724790: sched_switch: task bash:2289 [120] ==> sshd:2287 [120] <...>-2287 [000] 526276.725231: sched_switch: task sshd:2287 [120] ==> bash:2289 [120] <...>-2289 [000] 526276.725452: sched_switch: task bash:2289 [120] ==> sshd:2287 [120] <...>-2287 [000] 526276.727181: sched_switch: task sshd:2287 [120] ==> swapper:0 [140] <idle>-0 [000] 526277.032734: sched_switch: task swapper:0 [140] ==> events/0:5 [115] <...>-5 [000] 526277.032782: sched_switch: task events/0:5 [115] ==> swapper:0 [140] ... After this patch: # tracer: nop # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | bash-2269 [000] 527347.989229: sched_switch: task bash:2269 [120] ==> sshd:2267 [120] sshd-2267 [000] 527347.990960: sched_switch: task sshd:2267 [120] ==> bash:2269 [120] bash-2269 [000] 527347.991143: sched_switch: task bash:2269 [120] ==> sshd:2267 [120] sshd-2267 [000] 527347.992959: sched_switch: task sshd:2267 [120] ==> swapper:0 [140] <idle>-0 [000] 527348.531989: sched_switch: task swapper:0 [140] ==> events/0:5 [115] events/0-5 [000] 527348.532115: sched_switch: task events/0:5 [115] ==> swapper:0 [140] ... Changelog: v1->v2: Update Kconfig to select CONTEXT_SWITCH_TRACER in ENABLE_EVENT_TRACING v2->v3: v2 can solve problem that was caused by config EVENT_TRACING alone, but when CONFIG_FTRACE is off and CONFIG_TRACING is selected by other config, compile fail happened again. This version solves it. [ Impact: fix incomplete output of event tracing ] Signed-off-by:

Zhao Lei <zhaolei@cn.fujitsu.com> Cc: Tom Zanussi <tzanussi@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <4A14FDFE.2080402@cn.fujitsu.com> Signed-off-by:

Frederic Weisbecker <fweisbec@gmail.com>

kernel/trace/Kconfig

+7 −2

Original line number	Original line	Diff line number	Diff line
	@@ -49,6 +49,11 @@ config FTRACE_NMI_ENTER
	default y		default y

	config EVENT_TRACING		config EVENT_TRACING
			select CONTEXT_SWITCH_TRACER
			bool

			config CONTEXT_SWITCH_TRACER
			select MARKERS
	bool		bool

	config TRACING		config TRACING
	@@ -176,10 +181,10 @@ config SCHED_TRACER
	This tracer tracks the latency of the highest priority task		This tracer tracks the latency of the highest priority task
	to be scheduled in, starting from the point it has woken up.		to be scheduled in, starting from the point it has woken up.

	config CONTEXT_SWITCH_TRACER		config ENABLE_CONTEXT_SWITCH_TRACER
	bool "Trace process context switches"		bool "Trace process context switches"
	select TRACING		select TRACING
	select MARKERS		select CONTEXT_SWITCH_TRACER
	help		help
	This tracer gets called from the context switch and records		This tracer gets called from the context switch and records
	all switching of tasks.		all switching of tasks.

kernel/trace/trace_events.c

+6 −0

Original line number	Original line	Diff line number	Diff line
	@@ -85,6 +85,7 @@ static void ftrace_clear_events(void)

	if (call->enabled) {		if (call->enabled) {
	call->enabled = 0;		call->enabled = 0;
			tracing_stop_cmdline_record();
	call->unregfunc();		call->unregfunc();
	}		}
	}		}
	@@ -99,12 +100,14 @@ static void ftrace_event_enable_disable(struct ftrace_event_call *call,
	case 0:		case 0:
	if (call->enabled) {		if (call->enabled) {
	call->enabled = 0;		call->enabled = 0;
			tracing_stop_cmdline_record();
	call->unregfunc();		call->unregfunc();
	}		}
	break;		break;
	case 1:		case 1:
	if (!call->enabled) {		if (!call->enabled) {
	call->enabled = 1;		call->enabled = 1;
			tracing_start_cmdline_record();
	call->regfunc();		call->regfunc();
	}		}
	break;		break;
	@@ -1058,6 +1061,7 @@ static void trace_module_remove_events(struct module *mod)
	found = true;		found = true;
	if (call->enabled) {		if (call->enabled) {
	call->enabled = 0;		call->enabled = 0;
			tracing_stop_cmdline_record();
	call->unregfunc();		call->unregfunc();
	}		}
	if (call->event)		if (call->event)
	@@ -1262,11 +1266,13 @@ static __init void event_trace_self_tests(void)
	}		}

	call->enabled = 1;		call->enabled = 1;
			tracing_start_cmdline_record();
	call->regfunc();		call->regfunc();

	event_test_stuff();		event_test_stuff();

	call->unregfunc();		call->unregfunc();
			tracing_stop_cmdline_record();
	call->enabled = 0;		call->enabled = 0;

	pr_cont("OK\n");		pr_cont("OK\n");