1 #include <linux/module.h>
2 #include <linux/reboot.h>
3 #include <linux/init.h>
7 #include <linux/sched.h>
8 #include <linux/tboot.h>
9 #include <linux/delay.h>
10 #include <acpi/reboot.h>
15 #include <asm/pgtable.h>
16 #include <asm/proto.h>
17 #include <asm/reboot_fixups.h>
18 #include <asm/reboot.h>
19 #include <asm/pci_x86.h>
20 #include <asm/virtext.h>
25 # include <linux/ctype.h>
26 # include <linux/mc146818rtc.h>
28 # include <asm/x86_init.h>
32 * Power off function, if any
34 void (*pm_power_off)(void);
35 EXPORT_SYMBOL(pm_power_off);
37 static const struct desc_ptr no_idt = {};
38 static int reboot_mode;
39 enum reboot_type reboot_type = BOOT_ACPI;
42 #if defined(CONFIG_X86_32) && defined(CONFIG_SMP)
43 static int reboot_cpu = -1;
46 /* This is set if we need to go through the 'emergency' path.
47 * When machine_emergency_restart() is called, we may be on
48 * an inconsistent state and won't be able to do a clean cleanup
50 static int reboot_emergency;
52 /* This is set by the PCI code if either type 1 or type 2 PCI is detected */
53 bool port_cf9_safe = false;
55 /* reboot=b[ios] | s[mp] | t[riple] | k[bd] | e[fi] [, [w]arm | [c]old] | p[ci]
56 warm Don't set the cold reboot flag
57 cold Set the cold reboot flag
58 bios Reboot by jumping through the BIOS (only for X86_32)
59 smp Reboot by executing reset on BSP or other CPU (only for X86_32)
60 triple Force a triple fault (init)
61 kbd Use the keyboard controller. cold reset (default)
62 acpi Use the RESET_REG in the FADT
63 efi Use efi reset_system runtime service
64 pci Use the so-called "PCI reset register", CF9
65 force Avoid anything that could hang.
67 static int __init reboot_setup(char *str)
82 if (isdigit(*(str+1))) {
83 reboot_cpu = (int) (*(str+1) - '0');
84 if (isdigit(*(str+2)))
85 reboot_cpu = reboot_cpu*10 + (int)(*(str+2) - '0');
87 /* we will leave sorting out the final value
88 when we are ready to reboot, since we might not
89 have detected BSP APIC ID or smp_num_cpu */
91 #endif /* CONFIG_SMP */
108 str = strchr(str, ',');
117 __setup("reboot=", reboot_setup);
122 * Reboot options and system auto-detection code provided by
123 * Dell Inc. so their systems "just work". :-)
127 * Some machines require the "reboot=b" or "reboot=k" commandline options,
128 * this quirk makes that automatic.
130 static int __init set_bios_reboot(const struct dmi_system_id *d)
132 if (reboot_type != BOOT_BIOS) {
133 reboot_type = BOOT_BIOS;
134 printk(KERN_INFO "%s series board detected. Selecting BIOS-method for reboots.\n", d->ident);
139 static int __init set_kbd_reboot(const struct dmi_system_id *d)
141 if (reboot_type != BOOT_KBD) {
142 reboot_type = BOOT_KBD;
143 printk(KERN_INFO "%s series board detected. Selecting KBD-method for reboot.\n", d->ident);
148 static struct dmi_system_id __initdata reboot_dmi_table[] = {
149 { /* Handle problems with rebooting on Dell E520's */
150 .callback = set_bios_reboot,
151 .ident = "Dell E520",
153 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
154 DMI_MATCH(DMI_PRODUCT_NAME, "Dell DM061"),
157 { /* Handle problems with rebooting on Dell 1300's */
158 .callback = set_bios_reboot,
159 .ident = "Dell PowerEdge 1300",
161 DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
162 DMI_MATCH(DMI_PRODUCT_NAME, "PowerEdge 1300/"),
165 { /* Handle problems with rebooting on Dell 300's */
166 .callback = set_bios_reboot,
167 .ident = "Dell PowerEdge 300",
169 DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
170 DMI_MATCH(DMI_PRODUCT_NAME, "PowerEdge 300/"),
173 { /* Handle problems with rebooting on Dell Optiplex 745's SFF*/
174 .callback = set_bios_reboot,
175 .ident = "Dell OptiPlex 745",
177 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
178 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 745"),
181 { /* Handle problems with rebooting on Dell Optiplex 745's DFF*/
182 .callback = set_bios_reboot,
183 .ident = "Dell OptiPlex 745",
185 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
186 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 745"),
187 DMI_MATCH(DMI_BOARD_NAME, "0MM599"),
190 { /* Handle problems with rebooting on Dell Optiplex 745 with 0KW626 */
191 .callback = set_bios_reboot,
192 .ident = "Dell OptiPlex 745",
194 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
195 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 745"),
196 DMI_MATCH(DMI_BOARD_NAME, "0KW626"),
199 { /* Handle problems with rebooting on Dell Optiplex 330 with 0KP561 */
200 .callback = set_bios_reboot,
201 .ident = "Dell OptiPlex 330",
203 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
204 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 330"),
205 DMI_MATCH(DMI_BOARD_NAME, "0KP561"),
208 { /* Handle problems with rebooting on Dell Optiplex 360 with 0T656F */
209 .callback = set_bios_reboot,
210 .ident = "Dell OptiPlex 360",
212 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
213 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 360"),
214 DMI_MATCH(DMI_BOARD_NAME, "0T656F"),
217 { /* Handle problems with rebooting on Dell OptiPlex 760 with 0G919G*/
218 .callback = set_bios_reboot,
219 .ident = "Dell OptiPlex 760",
221 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
222 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 760"),
223 DMI_MATCH(DMI_BOARD_NAME, "0G919G"),
226 { /* Handle problems with rebooting on Dell 2400's */
227 .callback = set_bios_reboot,
228 .ident = "Dell PowerEdge 2400",
230 DMI_MATCH(DMI_SYS_VENDOR, "Dell Computer Corporation"),
231 DMI_MATCH(DMI_PRODUCT_NAME, "PowerEdge 2400"),
234 { /* Handle problems with rebooting on Dell T5400's */
235 .callback = set_bios_reboot,
236 .ident = "Dell Precision T5400",
238 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
239 DMI_MATCH(DMI_PRODUCT_NAME, "Precision WorkStation T5400"),
242 { /* Handle problems with rebooting on Dell T7400's */
243 .callback = set_bios_reboot,
244 .ident = "Dell Precision T7400",
246 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
247 DMI_MATCH(DMI_PRODUCT_NAME, "Precision WorkStation T7400"),
250 { /* Handle problems with rebooting on HP laptops */
251 .callback = set_bios_reboot,
252 .ident = "HP Compaq Laptop",
254 DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
255 DMI_MATCH(DMI_PRODUCT_NAME, "HP Compaq"),
258 { /* Handle problems with rebooting on Dell XPS710 */
259 .callback = set_bios_reboot,
260 .ident = "Dell XPS710",
262 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
263 DMI_MATCH(DMI_PRODUCT_NAME, "Dell XPS710"),
266 { /* Handle problems with rebooting on Dell DXP061 */
267 .callback = set_bios_reboot,
268 .ident = "Dell DXP061",
270 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
271 DMI_MATCH(DMI_PRODUCT_NAME, "Dell DXP061"),
274 { /* Handle problems with rebooting on Sony VGN-Z540N */
275 .callback = set_bios_reboot,
276 .ident = "Sony VGN-Z540N",
278 DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
279 DMI_MATCH(DMI_PRODUCT_NAME, "VGN-Z540N"),
282 { /* Handle problems with rebooting on ASUS P4S800 */
283 .callback = set_bios_reboot,
284 .ident = "ASUS P4S800",
286 DMI_MATCH(DMI_BOARD_VENDOR, "ASUSTeK Computer INC."),
287 DMI_MATCH(DMI_BOARD_NAME, "P4S800"),
290 { /* Handle reboot issue on Acer Aspire one */
291 .callback = set_kbd_reboot,
292 .ident = "Acer Aspire One A110",
294 DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
295 DMI_MATCH(DMI_PRODUCT_NAME, "AOA110"),
301 static int __init reboot_init(void)
303 dmi_check_system(reboot_dmi_table);
306 core_initcall(reboot_init);
308 extern const unsigned char machine_real_restart_asm[];
309 extern const u64 machine_real_restart_gdt[3];
311 void machine_real_restart(unsigned int type)
314 unsigned long restart_pa;
315 void (*restart_lowmem)(unsigned int);
320 /* Write zero to CMOS register number 0x0f, which the BIOS POST
321 routine will recognize as telling it to do a proper reboot. (Well
322 that's what this book in front of me says -- it may only apply to
323 the Phoenix BIOS though, it's not clear). At the same time,
324 disable NMIs by setting the top bit in the CMOS address register,
325 as we're about to do peculiar things to the CPU. I'm not sure if
326 `outb_p' is needed instead of just `outb'. Use it to be on the
327 safe side. (Yes, CMOS_WRITE does outb_p's. - Paul G.)
329 spin_lock(&rtc_lock);
330 CMOS_WRITE(0x00, 0x8f);
331 spin_unlock(&rtc_lock);
334 * Switch back to the initial page table.
336 load_cr3(initial_page_table);
338 /* Write 0x1234 to absolute memory location 0x472. The BIOS reads
339 this on booting to tell it to "Bypass memory test (also warm
340 boot)". This seems like a fairly standard thing that gets set by
341 REBOOT.COM programs, and the previous reset routine did this
343 *((unsigned short *)0x472) = reboot_mode;
345 /* Patch the GDT in the low memory trampoline */
346 lowmem_gdt = TRAMPOLINE_SYM(machine_real_restart_gdt);
348 restart_va = TRAMPOLINE_SYM(machine_real_restart_asm);
349 restart_pa = virt_to_phys(restart_va);
350 restart_lowmem = (void (*)(unsigned int))restart_pa;
352 /* GDT[0]: GDT self-pointer */
354 (u64)(sizeof(machine_real_restart_gdt) - 1) +
355 ((u64)virt_to_phys(lowmem_gdt) << 16);
356 /* GDT[1]: 64K real mode code segment */
358 GDT_ENTRY(0x009b, restart_pa, 0xffff);
360 /* Jump to the identity-mapped low memory code */
361 restart_lowmem(type);
363 #ifdef CONFIG_APM_MODULE
364 EXPORT_SYMBOL(machine_real_restart);
367 #endif /* CONFIG_X86_32 */
370 * Some Apple MacBook and MacBookPro's needs reboot=p to be able to reboot
372 static int __init set_pci_reboot(const struct dmi_system_id *d)
374 if (reboot_type != BOOT_CF9) {
375 reboot_type = BOOT_CF9;
376 printk(KERN_INFO "%s series board detected. "
377 "Selecting PCI-method for reboots.\n", d->ident);
382 static struct dmi_system_id __initdata pci_reboot_dmi_table[] = {
383 { /* Handle problems with rebooting on Apple MacBook5 */
384 .callback = set_pci_reboot,
385 .ident = "Apple MacBook5",
387 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
388 DMI_MATCH(DMI_PRODUCT_NAME, "MacBook5"),
391 { /* Handle problems with rebooting on Apple MacBookPro5 */
392 .callback = set_pci_reboot,
393 .ident = "Apple MacBookPro5",
395 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
396 DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro5"),
399 { /* Handle problems with rebooting on Apple Macmini3,1 */
400 .callback = set_pci_reboot,
401 .ident = "Apple Macmini3,1",
403 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
404 DMI_MATCH(DMI_PRODUCT_NAME, "Macmini3,1"),
407 { /* Handle problems with rebooting on the iMac9,1. */
408 .callback = set_pci_reboot,
409 .ident = "Apple iMac9,1",
411 DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
412 DMI_MATCH(DMI_PRODUCT_NAME, "iMac9,1"),
415 { /* Handle problems with rebooting on the Latitude E6320. */
416 .callback = set_pci_reboot,
417 .ident = "Dell Latitude E6320",
419 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
420 DMI_MATCH(DMI_PRODUCT_NAME, "Latitude E6320"),
423 { /* Handle problems with rebooting on the Latitude E5420. */
424 .callback = set_pci_reboot,
425 .ident = "Dell Latitude E5420",
427 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
428 DMI_MATCH(DMI_PRODUCT_NAME, "Latitude E5420"),
431 { /* Handle problems with rebooting on the Latitude E6420. */
432 .callback = set_pci_reboot,
433 .ident = "Dell Latitude E6420",
435 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
436 DMI_MATCH(DMI_PRODUCT_NAME, "Latitude E6420"),
439 { /* Handle problems with rebooting on the OptiPlex 990. */
440 .callback = set_pci_reboot,
441 .ident = "Dell OptiPlex 990",
443 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
444 DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 990"),
447 { /* Handle problems with rebooting on the Precision M6600. */
448 .callback = set_pci_reboot,
449 .ident = "Dell OptiPlex 990",
451 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
452 DMI_MATCH(DMI_PRODUCT_NAME, "Precision M6600"),
455 { /* Handle problems with rebooting on the Dell PowerEdge C6100. */
456 .callback = set_pci_reboot,
457 .ident = "Dell PowerEdge C6100",
459 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
460 DMI_MATCH(DMI_PRODUCT_NAME, "C6100"),
463 { /* Some C6100 machines were shipped with vendor being 'Dell'. */
464 .callback = set_pci_reboot,
465 .ident = "Dell PowerEdge C6100",
467 DMI_MATCH(DMI_SYS_VENDOR, "Dell"),
468 DMI_MATCH(DMI_PRODUCT_NAME, "C6100"),
471 { /* Handle problems with rebooting on the Precision M6600. */
472 .callback = set_pci_reboot,
473 .ident = "Dell OptiPlex 990",
475 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
476 DMI_MATCH(DMI_PRODUCT_NAME, "Precision M6600"),
479 { /* Handle problems with rebooting on the Dell PowerEdge C6100. */
480 .callback = set_pci_reboot,
481 .ident = "Dell PowerEdge C6100",
483 DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
484 DMI_MATCH(DMI_PRODUCT_NAME, "C6100"),
487 { /* Some C6100 machines were shipped with vendor being 'Dell'. */
488 .callback = set_pci_reboot,
489 .ident = "Dell PowerEdge C6100",
491 DMI_MATCH(DMI_SYS_VENDOR, "Dell"),
492 DMI_MATCH(DMI_PRODUCT_NAME, "C6100"),
498 static int __init pci_reboot_init(void)
500 dmi_check_system(pci_reboot_dmi_table);
503 core_initcall(pci_reboot_init);
505 static inline void kb_wait(void)
509 for (i = 0; i < 0x10000; i++) {
510 if ((inb(0x64) & 0x02) == 0)
516 static void vmxoff_nmi(int cpu, struct pt_regs *regs)
518 cpu_emergency_vmxoff();
521 /* Use NMIs as IPIs to tell all CPUs to disable virtualization
523 static void emergency_vmx_disable_all(void)
525 /* Just make sure we won't change CPUs while doing this */
528 /* We need to disable VMX on all CPUs before rebooting, otherwise
529 * we risk hanging up the machine, because the CPU ignore INIT
530 * signals when VMX is enabled.
532 * We can't take any locks and we may be on an inconsistent
533 * state, so we use NMIs as IPIs to tell the other CPUs to disable
536 * For safety, we will avoid running the nmi_shootdown_cpus()
537 * stuff unnecessarily, but we don't have a way to check
538 * if other CPUs have VMX enabled. So we will call it only if the
539 * CPU we are running on has VMX enabled.
541 * We will miss cases where VMX is not enabled on all CPUs. This
542 * shouldn't do much harm because KVM always enable VMX on all
543 * CPUs anyway. But we can miss it on the small window where KVM
544 * is still enabling VMX.
546 if (cpu_has_vmx() && cpu_vmx_enabled()) {
547 /* Disable VMX on this CPU.
551 /* Halt and disable VMX on the other CPUs */
552 nmi_shootdown_cpus(vmxoff_nmi);
558 void __attribute__((weak)) mach_reboot_fixups(void)
563 * Windows compatible x86 hardware expects the following on reboot:
565 * 1) If the FADT has the ACPI reboot register flag set, try it
566 * 2) If still alive, write to the keyboard controller
567 * 3) If still alive, write to the ACPI reboot register again
568 * 4) If still alive, write to the keyboard controller again
570 * If the machine is still alive at this stage, it gives up. We default to
571 * following the same pattern, except that if we're still alive after (4) we'll
572 * try to force a triple fault and then cycle between hitting the keyboard
573 * controller and doing that
575 static void native_machine_emergency_restart(void)
579 int orig_reboot_type = reboot_type;
581 if (reboot_emergency)
582 emergency_vmx_disable_all();
584 tboot_shutdown(TB_SHUTDOWN_REBOOT);
586 /* Tell the BIOS if we want cold or warm reboot */
587 *((unsigned short *)__va(0x472)) = reboot_mode;
590 /* Could also try the reset bit in the Hammer NB */
591 switch (reboot_type) {
593 mach_reboot_fixups(); /* for board specific fixups */
595 for (i = 0; i < 10; i++) {
598 outb(0xfe, 0x64); /* pulse reset low */
601 if (attempt == 0 && orig_reboot_type == BOOT_ACPI) {
603 reboot_type = BOOT_ACPI;
605 reboot_type = BOOT_TRIPLE;
611 __asm__ __volatile__("int3");
613 reboot_type = BOOT_KBD;
618 machine_real_restart(MRR_BIOS);
620 reboot_type = BOOT_KBD;
626 reboot_type = BOOT_KBD;
630 if (efi_enabled(EFI_RUNTIME_SERVICES))
631 efi.reset_system(reboot_mode ?
634 EFI_SUCCESS, 0, NULL);
635 reboot_type = BOOT_KBD;
639 port_cf9_safe = true;
644 u8 cf9 = inb(0xcf9) & ~6;
645 outb(cf9|2, 0xcf9); /* Request hard reset */
647 outb(cf9|6, 0xcf9); /* Actually do the reset */
650 reboot_type = BOOT_KBD;
656 void native_machine_shutdown(void)
658 /* Stop the cpus and apics */
661 /* The boot cpu is always logical cpu 0 */
662 int reboot_cpu_id = 0;
665 #ifdef CONFIG_X86_IO_APIC
672 /* See if there has been given a command line override */
673 if ((reboot_cpu != -1) && (reboot_cpu < nr_cpu_ids) &&
674 cpu_online(reboot_cpu))
675 reboot_cpu_id = reboot_cpu;
678 /* Make certain the cpu I'm about to reboot on is online */
679 if (!cpu_online(reboot_cpu_id))
680 reboot_cpu_id = smp_processor_id();
682 /* Make certain I only run on the appropriate processor */
683 set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id));
685 /* O.K Now that I'm on the appropriate processor,
686 * stop all of the others.
693 #ifdef CONFIG_HPET_TIMER
698 x86_platform.iommu_shutdown();
702 static void __machine_emergency_restart(int emergency)
704 reboot_emergency = emergency;
705 machine_ops.emergency_restart();
708 static void native_machine_restart(char *__unused)
710 printk("machine restart\n");
714 __machine_emergency_restart(0);
717 static void native_machine_halt(void)
719 /* stop other cpus and apics */
722 tboot_shutdown(TB_SHUTDOWN_HALT);
728 static void native_machine_power_off(void)
735 /* a fallback in case there is no PM info available */
736 tboot_shutdown(TB_SHUTDOWN_HALT);
739 struct machine_ops machine_ops = {
740 .power_off = native_machine_power_off,
741 .shutdown = native_machine_shutdown,
742 .emergency_restart = native_machine_emergency_restart,
743 .restart = native_machine_restart,
744 .halt = native_machine_halt,
746 .crash_shutdown = native_machine_crash_shutdown,
750 void machine_power_off(void)
752 machine_ops.power_off();
755 void machine_shutdown(void)
757 machine_ops.shutdown();
760 void machine_emergency_restart(void)
762 __machine_emergency_restart(1);
765 void machine_restart(char *cmd)
767 machine_ops.restart(cmd);
770 void machine_halt(void)
776 void machine_crash_shutdown(struct pt_regs *regs)
778 machine_ops.crash_shutdown(regs);
783 #if defined(CONFIG_SMP)
785 /* This keeps a track of which one is crashing cpu. */
786 static int crashing_cpu;
787 static nmi_shootdown_cb shootdown_callback;
789 static atomic_t waiting_for_crash_ipi;
791 static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
795 cpu = raw_smp_processor_id();
797 /* Don't do anything if this handler is invoked on crashing cpu.
798 * Otherwise, system will completely hang. Crashing cpu can get
799 * an NMI if system was initially booted with nmi_watchdog parameter.
801 if (cpu == crashing_cpu)
805 shootdown_callback(cpu, regs);
807 atomic_dec(&waiting_for_crash_ipi);
808 /* Assume hlt works */
816 static void smp_send_nmi_allbutself(void)
818 apic->send_IPI_allbutself(NMI_VECTOR);
821 /* Halt all other CPUs, calling the specified function on each of them
823 * This function can be used to halt all other CPUs on crash
824 * or emergency reboot time. The function passed as parameter
825 * will be called inside a NMI handler on all CPUs.
827 void nmi_shootdown_cpus(nmi_shootdown_cb callback)
832 /* Make a note of crashing cpu. Will be used in NMI callback.*/
833 crashing_cpu = safe_smp_processor_id();
835 shootdown_callback = callback;
837 atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
838 /* Would it be better to replace the trap vector here? */
839 if (register_nmi_handler(NMI_LOCAL, crash_nmi_callback,
840 NMI_FLAG_FIRST, "crash"))
841 return; /* return what? */
842 /* Ensure the new callback function is set before sending
847 smp_send_nmi_allbutself();
849 msecs = 1000; /* Wait at most a second for the other cpus to stop */
850 while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
855 /* Leave the nmi callback set */
857 #else /* !CONFIG_SMP */
858 void nmi_shootdown_cpus(nmi_shootdown_cb callback)
860 /* No other CPUs to shoot down */