[PATCH v3 0/2] ftrace: Add task_comm support for trace_event

[Zhaolei <zhaolei@cn.fujitsu.com>]

Hello,

Ingo pointed out that v2 patch still cause kernel compile fail:
kernel/built-in.o: In function `ftrace_event_enable_disable':
trace_events.c:(.text+0x4df08): undefined reference to `tracing_stop_cmdline_record'
trace_events.c:(.text+0x4df1f): undefined reference to `tracing_start_cmdline_record'

It is because CONFIG_TRACING is on(But CONFIG_FTRACE is off),
which compiles trace_events but leaves trace_sched_switch.
(Which is different with problem that I fixed in v1->v2)

Changelog:
v1->v2: Update Kconfig to select CONTEXT_SWITCH_TRACER in ENABLE_EVENT_TRACING
v2->v3: v2 can solve problem that 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.

Thanks
Zhaolei