linux-kernel - Re: [PATCH v2 1/2] tools lib traceevent: Export dynamic symbols used by traceevent plugins

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Date:	Thu, 14 May 2015 20:56:15 +0800
From:	He Kuang <hekuang@...wei.com>
To:	Jiri Olsa <jolsa@...hat.com>, hekuang <hekuang@...o.com>
CC:	<acme@...nel.org>, <jolsa@...nel.org>, <mingo@...hat.com>,
	<a.p.zijlstra@...llo.nl>, <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] tools lib traceevent: Export dynamic symbols used
 by traceevent plugins

Hi, jirka

On 2015/5/13 22:50, Jiri Olsa wrote:
> On Tue, May 12, 2015 at 11:25:45PM +0800, hekuang wrote:
>> Hi, jirka
>>
>> On 05/12/2015 08:37 PM, Jiri Olsa wrote:
>>> On Tue, May 12, 2015 at 06:41:56AM +0000, He Kuang wrote:
>>>
>>> SNIP
>>>
>>>>   	$(Q)$(MAKE) $(build)=perf
>>>> -$(OUTPUT)perf: $(PERFLIBS) $(PERF_IN)
>>>> -	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(PERF_IN) $(LIBS) -o $@
>>>> +LD_LIBTRACEEVENT_FLAGS += -Xlinker --dynamic-list=$(LIBTRACEEVENT_DYNAMIC_LIST)
>>>> +$(OUTPUT)perf: $(PERFLIBS) $(PERF_IN) $(LIBTRACEEVENT_DYNAMIC_LIST)
>>>> +	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $(LD_LIBTRACEEVENT_FLAGS) $(PERF_IN) $(LIBS) -o $@
>>>>   $(GTK_IN): FORCE
>>>>   	$(Q)$(MAKE) $(build)=gtk
>>>> @@ -373,7 +375,13 @@ $(LIB_FILE): $(LIBPERF_IN)
>>>>   LIBTRACEEVENT_FLAGS += plugin_dir=$(plugindir_SQ)
>>>>   $(LIBTRACEEVENT): FORCE
>>>> -	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent.a plugins
>>>> +	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent.a
>>>> +
>>>> +libtraceevent_plugins: FORCE
>>>> +	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) plugins
>>>> +
>>>> +$(LIBTRACEEVENT_DYNAMIC_LIST): libtraceevent_plugins
>>>> +	$(Q)$(MAKE) -C $(TRACE_EVENT_DIR) $(LIBTRACEEVENT_FLAGS) O=$(OUTPUT) $(OUTPUT)libtraceevent-dynamic-list
>>> I thought the idea of v2 was not to introduce new target,
>>> something like in attached patch (not completely tested)
>>>
>>> jirka
>>
>> There is a problem, the target perf executable is dependent on
>> the dynamic-list-file, so we should add plugins or the
>> dynamic-list-file to perf's dependencies.
>>
>> As your patch below, the dynamic-list-file is built implictly
>> when building plugins, so we should not add it directly to the
>> dependency list of perf.
>>
>> It seems new targets are needed. In the v2 patch,
>
> hum, I dont get it.. why ?
>
> dynamic-list-file gets rebuilt any time plugins are rebuilt..
> why not keep just the 'plugins' dependency?

You can test your patch as following steps:

$ touch ../lib/traceevent/plugin_function.c
$ make
   CC       plugin_function.o
   LD       plugin_function-in.o
   LINK     plugin_function.so
   GEN      libtraceevent-dynamic-list

perf is not rebuilt. There should be a 'GEN perf', right?

>
> jirka
>

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