Ackerley Tng <[email protected]> writes: > Lisa Wang <[email protected]> writes: > >> On Mon, Aug 24, 2026 at 03:00:47PM +0200, David Hildenbrand (Arm) wrote: >>> > +++ b/tools/testing/selftests/mm/memory-failure.c >>> > @@ -20,6 +20,10 @@ >>> > >>> > #include "vm_util.h" >>> > >>> > +#ifndef fallthrough >>> > +# define fallthrough __attribute__((__fallthrough__)) >>> > +#endif >>> >>> This doesn't belong into this test. >>> >>> rseq/rseq.c selftest already uses it. >>> >>> I think tools/testing/include/ already provides it. >>> >>> Maybe >>> >>> #include <linux/compiler.h> >>> >>> does the trick? >> >> Hi David, >> Thank you for replying. >> Would it be better to change it to /* FALLTHROUGH */ >> like the rest of the mm selftests? >> >> If we prefer to include <linux/compiler.h>, we can >> certainly do that, but we would also need to update >> the Makefile and fix a redefinition in pkey-helpers.h. >> >> --- a/tools/testing/selftests/mm/Makefile >> +++ b/tools/testing/selftests/mm/Makefile >> @@ -37,7 +37,7 @@ endif >> # LDLIBS. >> MAKEFLAGS += --no-builtin-rules >> >> -CFLAGS = -Wall -O2 -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) >> $(TOOLS_INCLUDES) >> +CFLAGS = -Wall -O2 -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) >> $(TOOLS_INCLUDES) -I$(top_srcdir)/tools/include >> CFLAGS += -Wunreachable-code >> LDLIBS = -lrt -lpthread -lm >> >> --- a/tools/testing/selftests/mm/pkey-helpers.h >> +++ b/tools/testing/selftests/mm/pkey-helpers.h >> @@ -22,7 +22,7 @@ >> typedef __u8 u8; >> typedef __u16 u16; >> typedef __u32 u32; >> -typedef __u64 u64; >> +// typedef __u64 u64; > > Removing this u64 typedef seems to be unrelated, the layers of includes > probably has some weirdness that needs to be ironed out. > > If the weirdness is not too complex to iron out to be in time for 7.4, I > think we can iron that out, if not perhaps using /* FALLTHROUGH */ is > fine, to be aligned with the other mm selftests. >
Lisa did some more investigation, and we discussed too. Here's my understanding: TOOLS_INCLUDES in the Makefile points to tools/include/uapi, which provides underscored types like __u64 to avoid polluting userspace symbol names. That makes sense since tools/include/uapi is generally copied from usr/include/ that is generated at build time, and usr/include/ is used by userspace programs in general. selftests are a special case of userspace programs, and since we want selftests to look similar to the kernel, we want to use u64 instead of __u64. While the kernel uses include/linux/types.h, the tools subsystem provides its own userspace compatibility header at tools/include/linux/types.h defining u64. Hence: 1. tools/include/uapi/linux/types.h provides __u64. 2. tools/include/linux/types.h provides u64. Adding -I$(top_srcdir)/tools/include switches from 1 to 2, causing definition conflicts in the mm selftests and more warnings. Since adding the tools/include path to use tools/include/linux/compiler.h breaks existing definitions, my vote is to use the comment-style fallthrough like the other mm selftests and clean up in a separate patch series. >> >> >> Lisa
