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-rwxr-xr-xtools/testing/selftests/rcutorture/bin/mkinitrd.sh27
1 files changed, 17 insertions, 10 deletions
diff --git a/tools/testing/selftests/rcutorture/bin/mkinitrd.sh b/tools/testing/selftests/rcutorture/bin/mkinitrd.sh
index da298394daa2..83552bb007b4 100755
--- a/tools/testing/selftests/rcutorture/bin/mkinitrd.sh
+++ b/tools/testing/selftests/rcutorture/bin/mkinitrd.sh
@@ -40,17 +40,24 @@ mkdir $T
cat > $T/init << '__EOF___'
#!/bin/sh
# Run in userspace a few milliseconds every second. This helps to
-# exercise the NO_HZ_FULL portions of RCU.
+# exercise the NO_HZ_FULL portions of RCU. The 192 instances of "a" was
+# empirically shown to give a nice multi-millisecond burst of user-mode
+# execution on a 2GHz CPU, as desired. Modern CPUs will vary from a
+# couple of milliseconds up to perhaps 100 milliseconds, which is an
+# acceptable range.
+#
+# Why not calibrate an exact delay? Because within this initrd, we
+# are restricted to Bourne-shell builtins, which as far as I know do not
+# provide any means of obtaining a fine-grained timestamp.
+
+a4="a a a a"
+a16="$a4 $a4 $a4 $a4"
+a64="$a16 $a16 $a16 $a16"
+a192="$a64 $a64 $a64"
while :
do
q=
- for i in \
- a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \
- a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \
- a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \
- a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \
- a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a \
- a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a
+ for i in $a192
do
q="$q $i"
done
@@ -124,8 +131,8 @@ if echo -e "#if __x86_64__||__i386__||__i486__||__i586__||__i686__" \
| grep -q '^yes'; then
# architecture supported by nolibc
${CROSS_COMPILE}gcc -fno-asynchronous-unwind-tables -fno-ident \
- -nostdlib -include ../bin/nolibc.h -lgcc -s -static -Os \
- -o init init.c
+ -nostdlib -include ../../../../include/nolibc/nolibc.h \
+ -lgcc -s -static -Os -o init init.c
else
${CROSS_COMPILE}gcc -s -static -Os -o init init.c
fi