samples/watch_queue/Makefile specifies the header search path -I$(objtree)/usr/include, which is probaby needed to include <linux/watch_queue.h> etc.
To make it work properly, add "depends on HEADERS_INSTALL" so that headers are installed into $(objtree)/usr/include before building this sample. Fixes: 7141642ed120 ("Add sample notification program") Reported-by: Arnd Bergmann <a...@arndb.de> Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com> --- Arnd reported a build error: https://lkml.org/lkml/2019/9/6/665 Missing "depends on HEADERS_INSTALL" is the only reason I have in my mind. If it still fails to build, I do not know why. samples/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/samples/Kconfig b/samples/Kconfig index 2c3e07addd38..d0761f29ccb0 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -171,6 +171,7 @@ config SAMPLE_VFS config SAMPLE_WATCH_QUEUE bool "Build example /dev/watch_queue notification consumer" + depends on HEADERS_INSTALL help Build example userspace program to use the new mount_notify(), sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function. -- 2.17.1