linux-kernel - Re: tools build: Unused function, incomplete rename

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Date:	Fri, 18 Sep 2015 17:42:47 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	David Ahern <dsahern@...il.com>,
	Wang Nan <wangnan0@...wei.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: tools build: Unused function, incomplete rename

Em Fri, Sep 18, 2015 at 04:48:52PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Sep 18, 2015 at 04:38:42PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Fri, Sep 18, 2015 at 04:23:34PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > 	While trying to figure out why the bpf feature test is always
> > > triggering the display of the "Auto-detecting system features" I noticed
> > > this pattern:
>  
> > Another problem, this time in how tools/lib/bpf/ specifies which
> > features to test for and which ones should have the feature detection
> > shown, does the following patch makes sense? I think it does because
> > FEATURE_TESTS looks like the ones that will be tested, and
> > FEATURE_DISPLAY the ones that will appear...:
> 
> So the original problem seems to be this:
> 
>   [acme@...icio linux]$ cat /tmp/build/perf/FEATURE-DUMP 
>   feature-libelf(1) feature-libelf-getphdrnum(1) feature-libelf-mmap(1) feature-bpf(1)
> 
> This is the content at the end of a build, i.e. the FEATURE-DUMP for
> tools/lib/ebpf/ usage of the feature detection system, since
> tools/perf/ uses the same file and selects a different set of
> features.
> 
> I think that ebpf should use a separate directory, inside $(OUTPUT),
> this way we would have $(OUTPUT)/FEATURE-DUMP for perf and
> $(OUTPUT)/bpf/FEATURE-DUMP for ebpf.

[acme@...icio linux]$ ls -la /tmp/build/perf/FEATURE-DUMP
-rw-rw-r--. 1 acme acme 338 Sep 18 17:38 /tmp/build/perf/FEATURE-DUMP
[acme@...icio linux]$ ls -la /tmp/build/perf/FEATURE-DUMP.libbpf 
-rw-rw-r--. 1 acme acme 85 Sep 18 17:38 /tmp/build/perf/FEATURE-DUMP.libbpf
[acme@...icio linux]$

Ok, patch below fixes this one, now the second run doesn't auto detects
things again, i.e. libbpf feature detection doesn't stomps on perf's,
I'll get those patches in a patchkit and send over the weekend. If you
find anything fishy with it, holler.

- Arnaldo

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 0caeaf2cae5f..0dedb3d245a1 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -123,8 +123,9 @@ define feature_print_text_code
     MSG = $(shell printf '...%30s: %s' $(1) $(2))
 endef
 
+FEATURE_DUMP_FILENAME = $(OUTPUT)FEATURE-DUMP$(FEATURE_USER)
 FEATURE_DUMP := $(foreach feat,$(FEATURE_DISPLAY),feature-$(feat)($(feature-$(feat))))
-FEATURE_DUMP_FILE := $(shell touch $(OUTPUT)FEATURE-DUMP; cat $(OUTPUT)FEATURE-DUMP)
+FEATURE_DUMP_FILE := $(shell touch $(FEATURE_DUMP_FILENAME); cat $(FEATURE_DUMP_FILENAME))
 
 ifeq ($(dwarf-post-unwind),1)
   FEATURE_DUMP += dwarf-post-unwind($(dwarf-post-unwind-text))
@@ -138,6 +139,6 @@ endif
 # - VF is enabled
 
 ifneq ("$(FEATURE_DUMP)","$(FEATURE_DUMP_FILE)")
-  $(shell echo "$(FEATURE_DUMP)" > $(OUTPUT)FEATURE-DUMP)
+  $(shell echo "$(FEATURE_DUMP)" > $(FEATURE_DUMP_FILENAME))
   feature_display := 1
 endif
diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index f68d23a0b487..01b4ff16a4e0 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -64,8 +64,8 @@ srctree := $(patsubst %/,%,$(dir $(srctree)))
 #$(info Determined 'srctree' to be $(srctree))
 endif
 
+FEATURE_USER = .libbpf
 FEATURE_DISPLAY = libelf libelf-getphdrnum libelf-mmap bpf
 FEATURE_TESTS = libelf bpf
 
 INCLUDES = -I. -I$(srctree)/tools/include -I$(srctree)/arch/$(ARCH)/include/uapi -I$(srctree)/include/uapi
 FEATURE_CHECK_CFLAGS-bpf = $(INCLUDES)


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