* gdbthread.h (currently_stepping): New declaration. * infrun.c (currently_stepping): Remove the forward declaration. (currently_stepping): Make it global. * linux-nat.c (resume_callback) <lp->stopped && lp->status == 0>: New variables tp and step, initialized them. Pass STEP to to_resume. Print also possibly "PTRACE_SINGLESTEP" if STEP. Initialize LP->STEP. * remote.c (currently_stepping_callback): New. (remote_vcont_resume) <ptid_equal (ptid, minus_one_ptid) || ptid_is_pid (ptid)>: New variable tp. Call currently_stepping_callback and step such thread. gdb/testsuite/ * gdb.threads/sigstep-threads.exp: New file. * gdb.threads/sigstep-threads.c: New file.