rcutorture: Dispense with Dracut for initrd creation

    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