linux-kernel - [PATCH tip/core/rcu 02/12] rcutorture: Dispense with Dracut for initrd creation

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Date:   Mon,  9 Dec 2019 19:42:07 -0800
From:   paulmck@...nel.org
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH tip/core/rcu 02/12] rcutorture: Dispense with Dracut for initrd creation

From: "Paul E. McKenney" <paulmck@...nel.org>

The dracut scripting does not work on all platforms, and there are no
known failures from the init binary based on the statically linked C
program.  This commit therefore removes the dracut scripting so that the
statically linked C program is always used to create the init "script".

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 tools/testing/selftests/rcutorture/bin/mkinitrd.sh | 55 ++--------------------
 1 file changed, 3 insertions(+), 52 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/mkinitrd.sh b/tools/testing/selftests/rcutorture/bin/mkinitrd.sh
index 6fa9bd1..38e424d 100755
--- a/tools/testing/selftests/rcutorture/bin/mkinitrd.sh
+++ b/tools/testing/selftests/rcutorture/bin/mkinitrd.sh
@@ -20,58 +20,9 @@ if [ -s "$D/initrd/init" ]; then
     exit 0
 fi
 
-T=${TMPDIR-/tmp}/mkinitrd.sh.$$
-trap 'rm -rf $T' 0 2
-mkdir $T
-
-cat > $T/init << '__EOF___'
-#!/bin/sh
-# Run in userspace a few milliseconds every second.  This helps to
-# exercise the NO_HZ_FULL portions of RCU.  The 192 instances of "a" was
-# empirically shown to give a nice multi-millisecond burst of user-mode
-# execution on a 2GHz CPU, as desired.  Modern CPUs will vary from a
-# couple of milliseconds up to perhaps 100 milliseconds, which is an
-# acceptable range.
-#
-# Why not calibrate an exact delay?  Because within this initrd, we
-# are restricted to Bourne-shell builtins, which as far as I know do not
-# provide any means of obtaining a fine-grained timestamp.
-
-a4="a a a a"
-a16="$a4 $a4 $a4 $a4"
-a64="$a16 $a16 $a16 $a16"
-a192="$a64 $a64 $a64"
-while :
-do
-	q=
-	for i in $a192
-	do
-		q="$q $i"
-	done
-	sleep 1
-done
-__EOF___
-
-# Try using dracut to create initrd
-if command -v dracut >/dev/null 2>&1
-then
-	echo Creating $D/initrd using dracut.
-	# Filesystem creation
-	dracut --force --no-hostonly --no-hostonly-cmdline --module "base" $T/initramfs.img
-	cd $D
-	mkdir -p initrd
-	cd initrd
-	zcat $T/initramfs.img | cpio -id
-	cp $T/init init
-	chmod +x init
-	echo Done creating $D/initrd using dracut
-	exit 0
-fi
-
-# No dracut, so create a C-language initrd/init program and statically
-# link it.  This results in a very small initrd, but might be a bit less
-# future-proof than dracut.
-echo "Could not find dracut, attempting C initrd"
+# Create a C-language initrd/init infinite-loop program and statically
+# link it.  This results in a very small initrd.
+echo "Creating a statically linked C-language initrd"
 cd $D
 mkdir -p initrd
 cd initrd
-- 
2.9.5