arm64 tools build failure wrt smp_load_{acquire,release} expansion on gcc version 5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9)

So I noticed the following build failure thare point to:

commit 09d62154f61316f7e97eae3f31ef8770c7e4b386

Author: Daniel Borkmann <[email protected]>
Date:   Fri Oct 19 15:51:02 2018 +0200

tools, perf: add and use optimized ring_buffer_{read_head, write_tail} helpers

-------------------------

50 ubuntu:16.04-x-arm64 : FAIL aarch64-linux-gnu-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609

Works well with:

59 ubuntu:18.04-x-arm64 : Ok aarch64-linux-gnu-gcc (Ubuntu/Linaro 7.3.0-27ubuntu1~18.04) 7.3.0

And all the other environments I test build :-)

Peter, do you recall something simple that could fix this?

- Arnaldo

[root@seventh linux-perf-tools-build]# cat /tmp/dm.log/ubuntu\:16.04-x-arm64 ubuntu:16.04-x-arm64
Downloading http://192.168.86.4/perf/perf-4.19.0.tar.xz...

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed

100 1388k 100 1388k 0 0 82.9M 0 --:--:-- --:--:-- --:--:-- 90.3M
e8eb3b801d8447b247f48e501e7d555384950388
Using built-in specs.
COLLECT_GCC=aarch64-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/aarch64-linux-gnu/5/lto-wrapper
Target: aarch64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9' --with-bugurl=file:///usr/share/doc/gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libquadmath --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-5-arm64-cross/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-5-arm64-cross --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-arm64-cross --with-arch-directory=aarch64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libgcj --enable-multiarch --enable-fix-cortex-a53-843419 --disable-werror --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=aarch64-linux-gnu --program-prefix=aarch64-linux-gnu- --includedir=/usr/aarch64-linux-gnu/include Thread model: posix
gcc version 5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9)
make: Entering directory '/git/linux/tools/perf'

  BUILD:   Doing 'make -j4' parallel build
  HOSTCC   /tmp/build/perf/fixdep.o
  HOSTLD   /tmp/build/perf/fixdep-in.o
  LINK     /tmp/build/perf/fixdep

sh: 1: command: Illegal option -c

Auto-detecting system features:

...                         dwarf: [ on  ]
...            dwarf_getlocations: [ on  ]
...                         glibc: [ on  ]

... gtk2: [ OFF ]
... libaudit: [ OFF ]
... libbfd: [ OFF ]
... libelf: [ on ]
... libnuma: [ OFF ]
... numa_num_possible_cpus: [ OFF ]
... libperl: [ OFF ]
... libpython: [ OFF ]
... libslang: [ OFF ]
... libcrypto: [ OFF ]
... libunwind: [ OFF ]
... libdw-dwarf-unwind: [ on ]
... zlib: [ on ]
... lzma: [ OFF ]
... get_cpuid: [ OFF ]
... bpf: [ on ]

Makefile.config:445: No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev Makefile.config:491: No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR Makefile.config:583: No libcrypto.h found, disables jitted code injection, please install libssl-devel or libssl-dev Makefile.config:598: slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev Makefile.config:612: GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev Makefile.config:639: Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev Makefile.config:666: No python interpreter was found: disables Python support - please install python-devel/python-dev Makefile.config:721: No bfd.h/libbfd found, please install binutils-dev[el]/zlib-static/libiberty-dev to gain symbol demangling Makefile.config:750: No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev Makefile.config:763: No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev Makefile.config:814: No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev Makefile.config:840: No alternatives command found, you need to set JDIR= to point to the root of your Java directory
GEN /tmp/build/perf/common-cmds.h
PERF_VERSION = 4.19.ge8eb3b8
<SNIP>

  CC       /tmp/build/perf/plugin_sched_switch.o
  CC       /tmp/build/perf/util/annotate.o
  LD       /tmp/build/perf/plugin_mac80211-in.o
  CC       /tmp/build/perf/plugin_function.o
  LD       /tmp/build/perf/plugin_kvm-in.o
  CC       /tmp/build/perf/plugin_xen.o
  LD       /tmp/build/perf/plugin_sched_switch-in.o
  CC       /tmp/build/perf/arch/common.o
  LD       /tmp/build/perf/plugin_function-in.o
  LD       /tmp/build/perf/plugin_xen-in.o
  MKDIR    /tmp/build/perf/ui/
  CC       /tmp/build/perf/ui/setup.o
  CC       /tmp/build/perf/plugin_scsi.o
In file included from /git/linux/tools/include/asm/barrier.h:8:0,
                 from util/../perf-sys.h:11,
                 from util/../perf.h:18,
                 from util/symbol.h:9,
                 from util/sort.h:12,
                 from util/annotate.c:14:
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_read_head':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_write_tail':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
  smp_store_release(&base->data_tail, tail);
  ^
  LD       /tmp/build/perf/plugin_scsi-in.o
  CC       /tmp/build/perf/plugin_cfg80211.o
  LD       /tmp/build/perf/plugin_cfg80211-in.o
  LINK     /tmp/build/perf/plugin_jbd2.so
  MKDIR    /tmp/build/perf/arch/arm64/util/
  MKDIR    /tmp/build/perf/ui/
  LINK     /tmp/build/perf/plugin_hrtimer.so
  CC       /tmp/build/perf/arch/arm64/util/header.o
  CC       /tmp/build/perf/ui/helpline.o
  LINK     /tmp/build/perf/plugin_kmem.so
  LINK     /tmp/build/perf/plugin_kvm.so
  LINK     /tmp/build/perf/plugin_mac80211.so
  LINK     /tmp/build/perf/plugin_sched_switch.so
  LINK     /tmp/build/perf/plugin_function.so
  MKDIR    /tmp/build/perf/arch/arm64/util/
  CC       /tmp/build/perf/arch/arm64/util/sym-handling.o
  CC       /tmp/build/perf/ui/progress.o
  LINK     /tmp/build/perf/plugin_xen.so
  LINK     /tmp/build/perf/plugin_scsi.so
  LINK     /tmp/build/perf/plugin_cfg80211.so
  MKDIR    /tmp/build/perf/arch/arm64/tests/
  CC       /tmp/build/perf/arch/arm64/tests/regs_load.o
  CC       /tmp/build/perf/ui/util.o
  MKDIR    /tmp/build/perf/arch/arm64/tests/
  CC       /tmp/build/perf/arch/arm64/tests/dwarf-unwind.o
  CC       /tmp/build/perf/arch/arm64/util/dwarf-regs.o
  CC       /tmp/build/perf/ui/hist.o
  CC       /tmp/build/perf/arch/arm64/util/unwind-libdw.o
  CC       /tmp/build/perf/arch/arm64/tests/arch-tests.o
  LD       /tmp/build/perf/arch/arm64/tests/libperf-in.o
  MKDIR    /tmp/build/perf/arch/arm64/util/../../arm/util/
  CC       /tmp/build/perf/arch/arm64/util/../../arm/util/pmu.o
In file included from /git/linux/tools/include/asm/barrier.h:8:0,
                 from ui/../util/../perf-sys.h:11,
                 from ui/../util/../perf.h:18,
                 from ui/../util/callchain.h:5,
                 from ui/../util/hist.h:7,
                 from ui/hist.c:6:
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_read_head':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_write_tail':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
  smp_store_release(&base->data_tail, tail);
  ^
  MKDIR    /tmp/build/perf/arch/arm64/util/../../arm/util/
  CC       /tmp/build/perf/arch/arm64/util/../../arm/util/auxtrace.o
  CC       /tmp/build/perf/arch/arm64/util/../../arm/util/cs-etm.o
In file included from /git/linux/tools/include/asm/barrier.h:8:0,
                 from /git/linux/tools/perf/util/include/../../util/../perf-sys.h:11,
                 from /git/linux/tools/perf/util/include/../../util/../perf.h:18,
                 from /git/linux/tools/perf/util/include/../../util/auxtrace.h:28,
                 from arch/arm64/util/../../arm/util/auxtrace.c:10:
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_read_head':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_write_tail':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
In file included from /git/linux/tools/include/asm/barrier.h:8:0,

                 from /git/linux/tools/perf/util/include/../../util/../perf-sys.h:11,
                 from /git/linux/tools/perf/util/include/../../util/../perf.h:18,
                 from /git/linux/tools/perf/util/include/../../util/symbol.h:9,
                 from /git/linux/tools/perf/util/include/../../util/evsel.h:11,
                 from arch/arm64/util/../../arm/util/cs-etm.h:10,
                 from arch/arm64/util/../../arm/util/cs-etm.c:15:
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_read_head':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_write_tail':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/arch/arm64/util/../../arm/util/.auxtrace.o.tmp': No such file or directory /git/linux/tools/build/Makefile.build:96: recipe for target '/tmp/build/perf/arch/arm64/util/../../arm/util/auxtrace.o' failed make[6]: *** [/tmp/build/perf/arch/arm64/util/../../arm/util/auxtrace.o] Error 1
make[6]: *** Waiting for unfinished jobs....

  MKDIR    /tmp/build/perf/scripts/
  LD       /tmp/build/perf/scripts/libperf-in.o
  CC       /tmp/build/perf/trace/beauty/clone.o
  CC       /tmp/build/perf/trace/beauty/fcntl.o
  CC       /tmp/build/perf/trace/beauty/flock.o

cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/arch/arm64/util/../../arm/util/.cs-etm.o.tmp': No such file or directory /git/linux/tools/build/Makefile.build:96: recipe for target '/tmp/build/perf/arch/arm64/util/../../arm/util/cs-etm.o' failed make[6]: *** [/tmp/build/perf/arch/arm64/util/../../arm/util/cs-etm.o] Error 1 /git/linux/tools/build/Makefile.build:139: recipe for target 'util' failed
make[5]: *** [util] Error 2
/git/linux/tools/build/Makefile.build:139: recipe for target 'arm64' failed
make[4]: *** [arm64] Error 2
/git/linux/tools/build/Makefile.build:139: recipe for target 'arch' failed
make[3]: *** [arch] Error 2
make[3]: *** Waiting for unfinished jobs....

  CC       /tmp/build/perf/trace/beauty/kcmp.o
  CC       /tmp/build/perf/trace/beauty/mount_flags.o
  CC       /tmp/build/perf/trace/beauty/pkey_alloc.o
  CC       /tmp/build/perf/trace/beauty/prctl.o
  CC       /tmp/build/perf/trace/beauty/sockaddr.o
  CC       /tmp/build/perf/trace/beauty/socket.o
  CC       /tmp/build/perf/trace/beauty/statx.o
  MKDIR    /tmp/build/perf/ui/stdio/
  CC       /tmp/build/perf/ui/stdio/hist.o
  LD       /tmp/build/perf/trace/beauty/libperf-in.o
  CC       /tmp/build/perf/builtin-bench.o

cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/util/.annotate.o.tmp': No such file or directory /git/linux/tools/build/Makefile.build:96: recipe for target '/tmp/build/perf/util/annotate.o' failed make[4]: *** [/tmp/build/perf/util/annotate.o] Error 1 /git/linux/tools/build/Makefile.build:139: recipe for target 'util' failed
make[3]: *** [util] Error 2

  LINK     /tmp/build/perf/pmu-events/jevents
  GEN      /tmp/build/perf/libtraceevent-dynamic-list
  GEN      /tmp/build/perf/pmu-events/pmu-events.c
  CC       /tmp/build/perf/pmu-events/pmu-events.o
  LD       /tmp/build/perf/pmu-events/pmu-events-in.o
  CC       /tmp/build/perf/builtin-annotate.o
  CC       /tmp/build/perf/builtin-config.o
In file included from /git/linux/tools/include/asm/barrier.h:8:0,
                 from util/../perf-sys.h:11,
                 from util/../perf.h:18,
                 from util/symbol.h:9,
                 from builtin-annotate.c:16:
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_read_head':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_write_tail':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
CC /tmp/build/perf/builtin-diff.o
cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/ui/.hist.o.tmp': No such file or directory /git/linux/tools/build/Makefile.build:96: recipe for target '/tmp/build/perf/ui/hist.o' failed make[4]: *** [/tmp/build/perf/ui/hist.o] Error 1
make[4]: *** Waiting for unfinished jobs....
CC /tmp/build/perf/builtin-evlist.o
In file included from /git/linux/tools/include/asm/barrier.h:8:0,

                 from util/../perf-sys.h:11,
                 from util/../perf.h:18,
                 from util/event.h:9,
                 from util/debug.h:9,
                 from builtin-diff.c:10:
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_read_head':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_write_tail':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
In file included from /git/linux/tools/include/asm/barrier.h:8:0,

                 from perf-sys.h:11,
                 from perf.h:18,
                 from builtin-evlist.c:12:
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_read_head':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:56:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u;  \
        ^
/git/linux/tools/include/linux/ring_buffer.h:58:9: note: in expansion of macro 'smp_load_acquire'
  return smp_load_acquire(&base->data_head);
         ^
/git/linux/tools/include/linux/ring_buffer.h: In function 'ring_buffer_write_tail':
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
/git/linux/tools/include/asm/../../arch/arm64/include/asm/barrier.h:19:8: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]

  union { typeof(*p) __val; char __c[1]; } __u =  \
        ^

/git/linux/tools/include/linux/ring_buffer.h:70:2: note: in expansion of macro 'smp_store_release'
smp_store_release(&base->data_tail, tail);
^
cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/.builtin-annotate.o.tmp': No such file or directory /git/linux/tools/build/Makefile.build:96: recipe for target '/tmp/build/perf/builtin-annotate.o' failed make[3]: *** [/tmp/build/perf/builtin-annotate.o] Error 1
make[3]: *** Waiting for unfinished jobs.... /git/linux/tools/build/Makefile.build:139: recipe for target 'ui' failed
make[3]: *** [ui] Error 2
Makefile.perf:650: recipe for target '/tmp/build/perf/libperf-in.o' failed
make[2]: *** [/tmp/build/perf/libperf-in.o] Error 2
make[2]: *** Waiting for unfinished jobs....
cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/.builtin-evlist.o.tmp': No such file or directory /git/linux/tools/build/Makefile.build:96: recipe for target '/tmp/build/perf/builtin-evlist.o' failed make[3]: *** [/tmp/build/perf/builtin-evlist.o] Error 1
cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/.builtin-diff.o.tmp': No such file or directory /git/linux/tools/build/Makefile.build:96: recipe for target '/tmp/build/perf/builtin-diff.o' failed make[3]: *** [/tmp/build/perf/builtin-diff.o] Error 1
Makefile.perf:522: recipe for target '/tmp/build/perf/perf-in.o' failed
make[2]: *** [/tmp/build/perf/perf-in.o] Error 2
Makefile.perf:206: recipe for target 'sub-make' failed
make[1]: *** [sub-make] Error 2
Makefile:69: recipe for target 'all' failed
make: *** [all] Error 2
make: Leaving directory '/git/linux/tools/perf'
[root@seventh linux-perf-tools-build]#

Hi Arnaldo,

Cheers for reporting this. I managed to reproduce the build failure with gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1).

The code in question is the arm64 versions of smp_load_acquire() and smp_store_release(). Unlike other architectures, these are not built around READ_ONCE() and WRITE_ONCE() since we have instructions we can use instead of fences. Bringing our macros up-to-date with those (i.e. tweaking the union initialisation and using the special "uXX_alias_t" types) appears to fix the issue for me.

Diff below...

Will

--->8

index 12835ea0e417..378c051fa177 100644
@@ -14,74 +14,75 @@
 #define wmb()		asm volatile("dmb ishst" ::: "memory")
 #define rmb()		asm volatile("dmb ishld" ::: "memory")
 
-#define smp_store_release(p, v)					\
-do {								\
-	union { typeof(*p) __val; char __c[1]; } __u =		\
-		{ .__val = (__force typeof(*p)) (v) }; 		\
-								\
-	switch (sizeof(*p)) {					\
-	case 1:							\
-		asm volatile ("stlrb %w1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u8 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	case 2:							\
-		asm volatile ("stlrh %w1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u16 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	case 4:							\
-		asm volatile ("stlr %w1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u32 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	case 8:							\
-		asm volatile ("stlr %1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u64 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	default:						\
-		/* Only to shut up gcc ... */			\
-		mb();						\
-		break;						\
-	}							\
+#define smp_store_release(p, v)						\
+do {									\
+	union { typeof(*p) __val; char __c[1]; } __u =			\
+		{ .__val = (v) }; 					\
+									\
+	switch (sizeof(*p)) {						\
+	case 1:								\
+		asm volatile ("stlrb %w1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u8_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	case 2:								\
+		asm volatile ("stlrh %w1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u16_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	case 4:								\
+		asm volatile ("stlr %w1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u32_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	case 8:								\
+		asm volatile ("stlr %1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u64_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	default:							\
+		/* Only to shut up gcc ... */				\
+		mb();							\
+		break;							\
+	}								\
 } while (0)
 
-#define smp_load_acquire(p)					\
-({								\
-	union { typeof(*p) __val; char __c[1]; } __u;		\
-								\
-	switch (sizeof(*p)) {					\
-	case 1:							\
-		asm volatile ("ldarb %w0, %1"			\
-			: "=r" (*(__u8 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	case 2:							\
-		asm volatile ("ldarh %w0, %1"			\
-			: "=r" (*(__u16 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	case 4:							\
-		asm volatile ("ldar %w0, %1"			\
-			: "=r" (*(__u32 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	case 8:							\
-		asm volatile ("ldar %0, %1"			\
-			: "=r" (*(__u64 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	default:						\
-		/* Only to shut up gcc ... */			\
-		mb();						\
-		break;						\
-	}							\
-	__u.__val;						\
+#define smp_load_acquire(p)						\
+({									\
+	union { typeof(*p) __val; char __c[1]; } __u =			\
+		{ .__c = { 0 } };					\
+									\
+	switch (sizeof(*p)) {						\
+	case 1:								\
+		asm volatile ("ldarb %w0, %1"				\
+			: "=r" (*(__u8_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	case 2:								\
+		asm volatile ("ldarh %w0, %1"				\
+			: "=r" (*(__u16_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	case 4:								\
+		asm volatile ("ldar %w0, %1"				\
+			: "=r" (*(__u32_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	case 8:								\
+		asm volatile ("ldar %0, %1"				\
+			: "=r" (*(__u64_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	default:							\
+		/* Only to shut up gcc ... */				\
+		mb();							\
+		break;							\
+	}								\
+	__u.__val;							\
 })
 
 #endif /* _TOOLS_LINUX_ASM_AARCH64_BARRIER_H */

Urgh, sorry about that, I tested the patch with arm64 on Ubuntu 18.04 back then, but not 16.04. :(

I just gave this a spin on 16.04 and it resolves the build issue, thanks for the quick fix, Will!

Em Wed, Oct 31, 2018 at 07:08:29PM +0100, Daniel Borkmann escreveu:

It buildz, ship it:

# time dm android-ndk:r12b-arm \
	  android-ndk:r15c-arm \
	  debian:experimental-x-arm64 \
	  ubuntu:14.04.4-x-linaro-arm64 \
	  ubuntu:16.04-x-arm \
	  ubuntu:16.04-x-arm64 \
	  ubuntu:18.04-x-arm \
	  ubuntu:18.04-x-arm64
   1 android-ndk:r12b-arm          : Ok   arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
   2 android-ndk:r15c-arm          : Ok   arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
   3 debian:experimental-x-arm64   : Ok   aarch64-linux-gnu-gcc (Debian 8.2.0-7) 8.2.0
   4 ubuntu:14.04.4-x-linaro-arm64 : Ok   aarch64-linux-gnu-gcc (Linaro GCC 5.5-2017.10) 5.5.0
   5 ubuntu:16.04-x-arm            : Ok   arm-linux-gnueabihf-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
   6 ubuntu:16.04-x-arm64          : Ok   aarch64-linux-gnu-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
   7 ubuntu:18.04-x-arm            : Ok   arm-linux-gnueabihf-gcc (Ubuntu/Linaro 7.3.0-27ubuntu1~18.04) 7.3.0
   8 ubuntu:18.04-x-arm64          : Ok   aarch64-linux-gnu-gcc (Ubuntu/Linaro 7.3.0-27ubuntu1~18.04) 7.3.0
#

So I've added it to my tree as below, can I keep it like that?

Thanks,

- Arnaldo

commit 86b21876a75c912917ade1e2b3831501eb2e9e45

Author: Will Deacon <[email protected]>
Date:   Wed Oct 31 17:44:08 2018 +0000

tools headers barrier: Fix arm64 tools build failure wrt smp_load_{acquire,release}

Cheers for reporting this. I managed to reproduce the build failure with gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1).

The code in question is the arm64 versions of smp_load_acquire() and smp_store_release(). Unlike other architectures, these are not built around READ_ONCE() and WRITE_ONCE() since we have instructions we can use instead of fences. Bringing our macros up-to-date with those (i.e. tweaking the union initialisation and using the special "uXX_alias_t" types) appears to fix the issue for me.

index 12835ea0e417..378c051fa177 100644
@@ -14,74 +14,75 @@
 #define wmb()		asm volatile("dmb ishst" ::: "memory")
 #define rmb()		asm volatile("dmb ishld" ::: "memory")
 
-#define smp_store_release(p, v)					\
-do {								\
-	union { typeof(*p) __val; char __c[1]; } __u =		\
-		{ .__val = (__force typeof(*p)) (v) }; 		\
-								\
-	switch (sizeof(*p)) {					\
-	case 1:							\
-		asm volatile ("stlrb %w1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u8 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	case 2:							\
-		asm volatile ("stlrh %w1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u16 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	case 4:							\
-		asm volatile ("stlr %w1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u32 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	case 8:							\
-		asm volatile ("stlr %1, %0"			\
-				: "=Q" (*p)			\
-				: "r" (*(__u64 *)__u.__c)	\
-				: "memory");			\
-		break;						\
-	default:						\
-		/* Only to shut up gcc ... */			\
-		mb();						\
-		break;						\
-	}							\
+#define smp_store_release(p, v)						\
+do {									\
+	union { typeof(*p) __val; char __c[1]; } __u =			\
+		{ .__val = (v) }; 					\
+									\
+	switch (sizeof(*p)) {						\
+	case 1:								\
+		asm volatile ("stlrb %w1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u8_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	case 2:								\
+		asm volatile ("stlrh %w1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u16_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	case 4:								\
+		asm volatile ("stlr %w1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u32_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	case 8:								\
+		asm volatile ("stlr %1, %0"				\
+				: "=Q" (*p)				\
+				: "r" (*(__u64_alias_t *)__u.__c)	\
+				: "memory");				\
+		break;							\
+	default:							\
+		/* Only to shut up gcc ... */				\
+		mb();							\
+		break;							\
+	}								\
 } while (0)
 
-#define smp_load_acquire(p)					\
-({								\
-	union { typeof(*p) __val; char __c[1]; } __u;		\
-								\
-	switch (sizeof(*p)) {					\
-	case 1:							\
-		asm volatile ("ldarb %w0, %1"			\
-			: "=r" (*(__u8 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	case 2:							\
-		asm volatile ("ldarh %w0, %1"			\
-			: "=r" (*(__u16 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	case 4:							\
-		asm volatile ("ldar %w0, %1"			\
-			: "=r" (*(__u32 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	case 8:							\
-		asm volatile ("ldar %0, %1"			\
-			: "=r" (*(__u64 *)__u.__c)		\
-			: "Q" (*p) : "memory");			\
-		break;						\
-	default:						\
-		/* Only to shut up gcc ... */			\
-		mb();						\
-		break;						\
-	}							\
-	__u.__val;						\
+#define smp_load_acquire(p)						\
+({									\
+	union { typeof(*p) __val; char __c[1]; } __u =			\
+		{ .__c = { 0 } };					\
+									\
+	switch (sizeof(*p)) {						\
+	case 1:								\
+		asm volatile ("ldarb %w0, %1"				\
+			: "=r" (*(__u8_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	case 2:								\
+		asm volatile ("ldarh %w0, %1"				\
+			: "=r" (*(__u16_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	case 4:								\
+		asm volatile ("ldar %w0, %1"				\
+			: "=r" (*(__u32_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	case 8:								\
+		asm volatile ("ldar %0, %1"				\
+			: "=r" (*(__u64_alias_t *)__u.__c)		\
+			: "Q" (*p) : "memory");				\
+		break;							\
+	default:							\
+		/* Only to shut up gcc ... */				\
+		mb();							\
+		break;							\
+	}								\
+	__u.__val;							\
 })
 
 #endif /* _TOOLS_LINUX_ASM_AARCH64_BARRIER_H */

[apologies if you get this twice -- my GPU hung (!) whilst sending my
previous response]

Yup, thanks for turning it into a proper patch. Just to be explicit, here's my s-o-b:

Will