/usr/include/atomic_ops/ is in libatomic-ops-dev 7.2~alpha5+cvs20101124-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/atomic_ops/generalize-small.h
/usr/include/atomic_ops/generalize.h
/usr/include/atomic_ops/sysdeps/
/usr/include/atomic_ops/sysdeps/README
/usr/include/atomic_ops/sysdeps/acquire_release_volatile.h
/usr/include/atomic_ops/sysdeps/aligned_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/all_acquire_release_volatile.h
/usr/include/atomic_ops/sysdeps/all_aligned_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/all_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/ao_t_is_int.h
/usr/include/atomic_ops/sysdeps/armcc/
/usr/include/atomic_ops/sysdeps/armcc/arm_v6.h
/usr/include/atomic_ops/sysdeps/atomic_load_store.h
/usr/include/atomic_ops/sysdeps/char_acquire_release_volatile.h
/usr/include/atomic_ops/sysdeps/char_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/emul_cas.h
/usr/include/atomic_ops/sysdeps/gcc/
/usr/include/atomic_ops/sysdeps/gcc/alpha.h
/usr/include/atomic_ops/sysdeps/gcc/arm.h
/usr/include/atomic_ops/sysdeps/gcc/avr32.h
/usr/include/atomic_ops/sysdeps/gcc/cris.h
/usr/include/atomic_ops/sysdeps/gcc/hppa.h
/usr/include/atomic_ops/sysdeps/gcc/ia64.h
/usr/include/atomic_ops/sysdeps/gcc/m68k.h
/usr/include/atomic_ops/sysdeps/gcc/mips.h
/usr/include/atomic_ops/sysdeps/gcc/powerpc.h
/usr/include/atomic_ops/sysdeps/gcc/s390.h
/usr/include/atomic_ops/sysdeps/gcc/sh.h
/usr/include/atomic_ops/sysdeps/gcc/sparc.h
/usr/include/atomic_ops/sysdeps/gcc/x86.h
/usr/include/atomic_ops/sysdeps/gcc/x86_64.h
/usr/include/atomic_ops/sysdeps/generic_pthread.h
/usr/include/atomic_ops/sysdeps/hpc/
/usr/include/atomic_ops/sysdeps/hpc/hppa.h
/usr/include/atomic_ops/sysdeps/hpc/ia64.h
/usr/include/atomic_ops/sysdeps/ibmc/
/usr/include/atomic_ops/sysdeps/ibmc/powerpc.h
/usr/include/atomic_ops/sysdeps/icc/
/usr/include/atomic_ops/sysdeps/icc/ia64.h
/usr/include/atomic_ops/sysdeps/int_acquire_release_volatile.h
/usr/include/atomic_ops/sysdeps/int_aligned_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/int_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/msftc/
/usr/include/atomic_ops/sysdeps/msftc/arm.h
/usr/include/atomic_ops/sysdeps/msftc/common32_defs.h
/usr/include/atomic_ops/sysdeps/msftc/x86.h
/usr/include/atomic_ops/sysdeps/msftc/x86_64.h
/usr/include/atomic_ops/sysdeps/ordered.h
/usr/include/atomic_ops/sysdeps/ordered_except_wr.h
/usr/include/atomic_ops/sysdeps/read_ordered.h
/usr/include/atomic_ops/sysdeps/short_acquire_release_volatile.h
/usr/include/atomic_ops/sysdeps/short_aligned_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/short_atomic_load_store.h
/usr/include/atomic_ops/sysdeps/standard_ao_double_t.h
/usr/include/atomic_ops/sysdeps/sunc/
/usr/include/atomic_ops/sysdeps/sunc/sparc.h
/usr/include/atomic_ops/sysdeps/sunc/x86.h
/usr/include/atomic_ops/sysdeps/sunc/x86_64.h
/usr/include/atomic_ops/sysdeps/test_and_set_t_is_ao_t.h
/usr/include/atomic_ops/sysdeps/test_and_set_t_is_char.h