gdb/Changelog:
* aarch64-tdep.c (aarch64_software_single_step): New function.
(aarch64_gdbarch_init): Handle single stepping of atomic sequences
with aarch64_software_single_step.
gdb/testsuite/ChangeLog:
* gdb.arch/aarch64-atomic-inst.c: New file.
* gdb.arch/aarch64-atomic-inst.exp: New file.