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Subject[PATCH tip/core/rcu 02/12] rcutorture: Dispense with Dracut for initrd creation
From: "Paul E. McKenney" <>

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 <>
tools/testing/selftests/rcutorture/bin/ | 55 ++--------------------
1 file changed, 3 insertions(+), 52 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/ b/tools/testing/selftests/rcutorture/bin/
index 6fa9bd1..38e424d 100755
--- a/tools/testing/selftests/rcutorture/bin/
+++ b/tools/testing/selftests/rcutorture/bin/
@@ -20,58 +20,9 @@ if [ -s "$D/initrd/init" ]; then
exit 0

-trap 'rm -rf $T' 0 2
-mkdir $T
-cat > $T/init << '__EOF___'
-# Run in userspace a few milliseconds every second. This helps to
-# exercise the NO_HZ_FULL portions of RCU. The 192 instances of "a" was
-# empirically shown to give a nice multi-millisecond burst of user-mode
-# execution on a 2GHz CPU, as desired. Modern CPUs will vary from a
-# couple of milliseconds up to perhaps 100 milliseconds, which is an
-# acceptable range.
-# Why not calibrate an exact delay? Because within this initrd, we
-# are restricted to Bourne-shell builtins, which as far as I know do not
-# provide any means of obtaining a fine-grained timestamp.
-a4="a a a a"
-a16="$a4 $a4 $a4 $a4"
-a64="$a16 $a16 $a16 $a16"
-a192="$a64 $a64 $a64"
-while :
- q=
- for i in $a192
- do
- q="$q $i"
- done
- sleep 1
-# Try using dracut to create initrd
-if command -v dracut >/dev/null 2>&1
- 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
-# 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
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