From 825d487583089f9a33d31650c9c41f6474aab7fc Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Thu, 15 Mar 2018 16:56:20 -0400 Subject: [PATCH] kbuild: make scripts/adjust_autoksyms.sh robust against timestamp races 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: Thomas Lindroth Signed-off-by: Nicolas Pitre Tested-by: Thomas Lindroth Signed-off-by: Masahiro Yamada --- scripts/adjust_autoksyms.sh | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh index 513da1a4a2da..d67830e6e360 100755 --- a/scripts/adjust_autoksyms.sh +++ b/scripts/adjust_autoksyms.sh @@ -84,6 +84,13 @@ while read sympath; do depfile="include/config/ksym/${sympath}.h" mkdir -p "$(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" + done echo $((count += 1)) done | tail -1 ) changed=${changed:-0}