* regcache.c (struct regcache): Add ptid_t member.

(regcache_xmalloc): Initialize it.
	(regcache_cpy_no_passthrough): Do not refer to current_regcache.
	(regcache_dup): Likewise.
	(regcache_dup_no_passthrough): Likewise.
	(current_regcache): Make static.
	(registers_ptid): Remove variable.
	(get_thread_regcache): New function.
	(get_current_regcache): New function.
	(registers_changed): Implement by freeing current regcache.
	(regcache_raw_read): Do not refer to current_regcache.  Set
	inferior_ptid to regcache->ptid while calling target routines.
	(regcache_raw_write): Likewise.
	(regcache_raw_supply): Do not refer to current_regcache.
	(read_pc_pid): Use thread regcache.  Do not modify inferior_ptid.
	(write_pc_pid): Likewise.
	(build_regcache): Remove.
	(_initialize_regcache): Do not call DEPRECATED_REGISTER_GDBARCH_SWAP
	or deprecated_register_gdbarch_swap.  Do not initialize
	registers_ptid.
	* regcache.h (get_current_regcache): Add prototype.
	(get_thread_regcache): Likewise.
	(current_regcache): Remove declaration.

	* corelow.c (core_open): Replace current_regcache by
	get_current_regcache ().
	* frame.c (frame_pop): Likewise.
	(put_frame_register): Likewise.
	(get_current_frame, create_new_frame): Likewise.
	* mi/mi-main.c (mi_cmd_data_write_register_values): Likewise.
	* stack.c (return_command): Likewise.
	* infcall.c (call_function_by_hand): Likewise.
	* infrun.c (resume): Likewise.
	(save_inferior_status, restore_inferior_status): Likewise.
	* linux-fork.c (fork_load_infrun_state): Likewise.
	(fork_save_infrun_state): Likewise.
	* win32-nat.c (win32_resume): Likewise.
	* i386fbsd-nat.c (i386fbsd_resume): Likewise.
	* monitor.c (monitor_wait): Likewise.
	* remote.c (remote_wait): Likewise.
	* remote-mips.c (mips_wait): Likewise.

	* bsd-kvm.c (bsd_kvm_open): Likewise
	(bsd_kvm_proc_cmd, bsd_kvm_pcb_cmd): Likewise.
	* fbsd-nat.c (fbsd_make_corefile_notes): Likewise.
	* i386-linux-nat.c (i386_linux_resume): Likewise.
	* ia64-linux-nat.c (ia64_linux_insert_watchpoint): Likewise.
	(ia64_linux_stopped_data_address): Likewise.

	* frv-tdep.c (frv_fdpic_loadmap_addresses): Likewise.
	* m32c-tdep.c (m32c_virtual_frame_pointer): Likewise.
	* mep-tdep.c (current_me_module, current_options): Likewise.
	* mips-tdep.c (deprecated_mips_set_processor_regs_hack): Likewise.

	* linux-nat.c (linux_nat_do_thread_registers): Use thread
	regcache instead of current_regcache.  Call target_fetch_registers.
	(linux_nat_corefile_thread_callback): Update call site.
	(linux_nat_do_registers): Likewise.
	* procfs.c (procfs_do_thread_registers): Use thread regcache instead
	of current_regcache.
	(procfs_make_note_section): Likewise.
	* proc-service.c (ps_lgetregs, ps_lsetregs): Likewise.
	(ps_lgetfpregs, ps_lsetfpregs): Likewise.
	* sol-thread.c (ps_lgetregs, ps_lsetregs): Likewise.
	(ps_lgetfpregs, ps_lsetfpregs): Likewise.

gdb/win32-nat.c

@@ -1318,7 +1318,7 @@ win32_resume (ptid_t ptid, int step, enum target_signal sig)
       if (step)
 	{
 	  /* Single step by setting t bit */
-	  win32_fetch_inferior_registers (current_regcache, PS_REGNUM);
+	  win32_fetch_inferior_registers (get_current_regcache (), PS_REGNUM);
 	  th->context.EFlags |= FLAG_TRACE_BIT;
 	}