linux-kernel - [PATCH] tools: fix annoying "mkdir -p ..." logs when building tools in parallel

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Message-ID: <20250211003914.1866689-1-masahiroy@kernel.org>
Date: Tue, 11 Feb 2025 09:39:12 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Masahiro Yamada <masahiroy@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Borislav Petkov <bp@...e.de>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	bpf@...r.kernel.org
Subject: [PATCH] tools: fix annoying "mkdir -p ..." logs when building tools in parallel

When CONFIG_OBJTOOL=y or CONFIG_DEBUG_INFO_BTF=y, parallel builds
show awkward "mkdir -p ..." logs.

  $ make -j16
    [ snip ]
  mkdir -p /home/masahiro/ref/linux/tools/objtool && make O=/home/masahiro/ref/linux subdir=tools/objtool --no-print-directory -C objtool
  mkdir -p /home/masahiro/ref/linux/tools/bpf/resolve_btfids && make O=/home/masahiro/ref/linux subdir=tools/bpf/resolve_btfids --no-print-directory -C bpf/resolve_btfids

Defining MAKEFLAGS=<value> on the command line wipes out command line
switches from the resultant MAKEFLAGS definition, even though the command
line switches are active. [1]

The first word of $(MAKEFLAGS) is a possibly empty group of characters
representing single-letter options that take no argument. However, this
breaks if MAKEFLAGS=<value> is given on the command line.

The tools/ and tools/% targets set MAKEFLAGS=<value> on the command
line, which breaks the following code in tools/scripts/Makefile.include:

    short-opts := $(firstword -$(MAKEFLAGS))

If MAKEFLAGS really needs modification, it should be done through the
environment variable, as follows:

    MAKEFLAGS=<value> $(MAKE) ...

That said, I question whether modifying MAKEFLAGS is necessary here.
The only flag we might want to exclude is --no-print-directory, as the
tools build system changes the working directory. However, people might
find the "Entering/Leaving directory" logs annoying.

I simply removed the offending MAKEFLAGS=.

[1]: https://savannah.gnu.org/bugs/?62469

Fixes: a50e43332756 ("perf tools: Honor parallel jobs")
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 Makefile | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/Makefile b/Makefile
index 89628e354ca7..52207bcb1a9d 100644
--- a/Makefile
+++ b/Makefile
@@ -1421,18 +1421,13 @@ ifneq ($(wildcard $(resolve_btfids_O)),)
 	$(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(resolve_btfids_O) clean
 endif

-# Clear a bunch of variables before executing the submake
-ifeq ($(quiet),silent_)
-tools_silent=s
-endif
-
 tools/: FORCE
 	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/
+	$(Q)$(MAKE) LDFLAGS= O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/

 tools/%: FORCE
 	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*
+	$(Q)$(MAKE) LDFLAGS= O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*

 # ---------------------------------------------------------------------------
 # Kernel selftest
-- 
2.43.0