From f788aaeb0e13891dafe5cf92936a439a711a30ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=BD=D0=B0=D0=B1?= <nabijaczleweli@nabijaczleweli.xyz>
Date: Thu, 23 Dec 2021 21:26:19 +0100
Subject: [PATCH] config: check for parallel(1), use it for cstyle
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Before:
$ time make cstyle
real    0m23.118s
user    0m23.002s
sys     0m0.114s

After:
$ time make cstyle
real    0m4.577s
user    0m31.487s
sys     0m0.699s

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Issue #12899
---
 Makefile.am               | 7 ++++++-
 config/always-parallel.m4 | 8 ++++++++
 config/zfs-build.m4       | 1 +
 3 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 config/always-parallel.m4

diff --git a/Makefile.am b/Makefile.am
index 34fe16ce4..d4b75264d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -114,6 +114,11 @@ commitcheck:
 		${top_srcdir}/scripts/commitcheck.sh; \
 	fi
 
+if HAVE_PARALLEL
+cstyle_line = -print0 | parallel -X0 ${top_srcdir}/scripts/cstyle.pl -cpP {}
+else
+cstyle_line = -exec ${top_srcdir}/scripts/cstyle.pl -cpP {} +
+endif
 PHONY += cstyle
 cstyle:
 	@find ${top_srcdir} -name build -prune \
@@ -121,7 +126,7 @@ cstyle:
 		! -name 'zfs_config.*' ! -name '*.mod.c' \
 		! -name 'opt_global.h' ! -name '*_if*.h' \
 		! -path './module/zstd/lib/*' \
-		-exec ${top_srcdir}/scripts/cstyle.pl -cpP {} \+
+		$(cstyle_line)
 
 filter_executable = -exec test -x '{}' \; -print
 
diff --git a/config/always-parallel.m4 b/config/always-parallel.m4
new file mode 100644
index 000000000..c1f1ae78e
--- /dev/null
+++ b/config/always-parallel.m4
@@ -0,0 +1,8 @@
+dnl #
+dnl # Check if GNU parallel is available.
+dnl #
+AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_PARALLEL], [
+	AC_CHECK_PROG([PARALLEL], [parallel], [yes])
+
+	AM_CONDITIONAL([HAVE_PARALLEL], [test "x$PARALLEL" = "xyes"])
+])
diff --git a/config/zfs-build.m4 b/config/zfs-build.m4
index ec4a2026b..b1604eb9d 100644
--- a/config/zfs-build.m4
+++ b/config/zfs-build.m4
@@ -226,6 +226,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS], [
 	ZFS_AC_CONFIG_ALWAYS_SED
 	ZFS_AC_CONFIG_ALWAYS_CPPCHECK
 	ZFS_AC_CONFIG_ALWAYS_SHELLCHECK
+	ZFS_AC_CONFIG_ALWAYS_PARALLEL
 ])
 
 AC_DEFUN([ZFS_AC_CONFIG], [