Commit df17a340 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Greg Kroah-Hartman

kbuild: make scripts/ robust against timestamp races

[ Upstream commit 825d487583089f9a33d31650c9c41f6474aab7fc ]

Some filesystems have timestamps with coarse precision that may allow
for a recently built object file to have the same timestamp as the
updated time on one of its dependency files. When that happens, the
object file doesn't get rebuilt as it should.

This is especially the case on filesystems that don't have sub-second
time precision, such as ext3 or Ext4 with 128B inodes.

Let's prevent that by making sure updated dependency files have a newer
timestamp than the first file we created (i.e. autoksyms.h.tmpnew).
Reported-by: 's avatarThomas Lindroth <>
Signed-off-by: 's avatarNicolas Pitre <>
Tested-by: 's avatarThomas Lindroth <>
Signed-off-by: Masahiro Yamada's avatarMasahiro Yamada <>
Signed-off-by: 's avatarSasha Levin <>
Signed-off-by: 's avatarGreg Kroah-Hartman <>
parent 78e74099
......@@ -83,6 +83,13 @@ while read sympath; do
mkdir -p "$(dirname "$depfile")"
touch "$depfile"
# Filesystems with coarse time precision may create timestamps
# equal to the one from a file that was very recently built and that
# needs to be rebuild. Let's guard against that by making sure our
# dep files are always newer than the first file we created here.
while [ ! "$depfile" -nt "$new_ksyms_file" ]; do
touch "$depfile"
echo $((count += 1))
done | tail -1 )
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