arch/powerpc/kernel/smp.c

   1 /*
   2  * SMP support for ppc.
   3  *
   4  * Written by Cort Dougan (cort@cs.nmt.edu) borrowing a great
   5  * deal of code from the sparc and intel versions.
   6  *
   7  * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
   8  *
   9  * PowerPC-64 Support added by Dave Engebretsen, Peter Bergner, and
  10  * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
  11  *
  12  *      This program is free software; you can redistribute it and/or
  13  *      modify it under the terms of the GNU General Public License
  14  *      as published by the Free Software Foundation; either version
  15  *      2 of the License, or (at your option) any later version.
  16  */
  17
  18 #undef DEBUG
  19
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/sched.h>
  23 #include <linux/smp.h>
  24 #include <linux/interrupt.h>
  25 #include <linux/delay.h>
  26 #include <linux/init.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/cache.h>
  29 #include <linux/err.h>
  30 #include <linux/sysdev.h>
  31 #include <linux/cpu.h>
  32 #include <linux/notifier.h>
  33 #include <linux/topology.h>
  34
  35 #include <asm/ptrace.h>
  36 #include <asm/atomic.h>
  37 #include <asm/irq.h>
  38 #include <asm/page.h>
  39 #include <asm/pgtable.h>
  40 #include <asm/prom.h>
  41 #include <asm/smp.h>
  42 #include <asm/time.h>
  43 #include <asm/machdep.h>
  44 #include <asm/cputhreads.h>
  45 #include <asm/cputable.h>
  46 #include <asm/system.h>
  47 #include <asm/mpic.h>
  48 #include <asm/vdso_datapage.h>
  49 #ifdef CONFIG_PPC64
  50 #include <asm/paca.h>
  51 #endif
  52
  53 #ifdef DEBUG
  54 #include <asm/udbg.h>
  55 #define DBG(fmt...) udbg_printf(fmt)
  56 #else
  57 #define DBG(fmt...)
  58 #endif
  59
  60
  61 /* Store all idle threads, this can be reused instead of creating
  62 * a new thread. Also avoids complicated thread destroy functionality
  63 * for idle threads.
  64 */
  65 #ifdef CONFIG_HOTPLUG_CPU
  66 /*
  67  * Needed only for CONFIG_HOTPLUG_CPU because __cpuinitdata is
  68  * removed after init for !CONFIG_HOTPLUG_CPU.
  69  */
  70 static DEFINE_PER_CPU(struct task_struct *, idle_thread_array);
  71 #define get_idle_for_cpu(x)      (per_cpu(idle_thread_array, x))
  72 #define set_idle_for_cpu(x, p)   (per_cpu(idle_thread_array, x) = (p))
  73 #else
  74 static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ;
  75 #define get_idle_for_cpu(x)      (idle_thread_array[(x)])
  76 #define set_idle_for_cpu(x, p)   (idle_thread_array[(x)] = (p))
  77 #endif
  78
  79 struct thread_info *secondary_ti;
  80
  81 DEFINE_PER_CPU(cpumask_var_t, cpu_sibling_map);
  82 DEFINE_PER_CPU(cpumask_var_t, cpu_core_map);
  83
  84 EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);
  85 EXPORT_PER_CPU_SYMBOL(cpu_core_map);
  86
  87 /* SMP operations for this machine */
  88 struct smp_ops_t *smp_ops;
  89
  90 /* Can't be static due to PowerMac hackery */
  91 volatile unsigned int cpu_callin_map[NR_CPUS];
  92
  93 int smt_enabled_at_boot = 1;
  94
  95 static void (*crash_ipi_function_ptr)(struct pt_regs *) = NULL;
  96
  97 #ifdef CONFIG_PPC64
  98 void __devinit smp_generic_kick_cpu(int nr)
  99 {
 100         BUG_ON(nr < 0 || nr >= NR_CPUS);
 101
 102         /*
 103          * The processor is currently spinning, waiting for the
 104          * cpu_start field to become non-zero After we set cpu_start,
 105          * the processor will continue on to secondary_start
 106          */
 107         paca[nr].cpu_start = 1;
 108         smp_mb();
 109 }
 110 #endif
 111
 112 void smp_message_recv(int msg)
 113 {
 114         switch(msg) {
 115         case PPC_MSG_CALL_FUNCTION:
 116                 generic_smp_call_function_interrupt();
 117                 break;
 118         case PPC_MSG_RESCHEDULE:
 119                 /* we notice need_resched on exit */
 120                 break;
 121         case PPC_MSG_CALL_FUNC_SINGLE:
 122                 generic_smp_call_function_single_interrupt();
 123                 break;
 124         case PPC_MSG_DEBUGGER_BREAK:
 125                 if (crash_ipi_function_ptr) {
 126                         crash_ipi_function_ptr(get_irq_regs());
 127                         break;
 128                 }
 129 #ifdef CONFIG_DEBUGGER
 130                 debugger_ipi(get_irq_regs());
 131                 break;
 132 #endif /* CONFIG_DEBUGGER */
 133                 /* FALLTHROUGH */
 134         default:
 135                 printk("SMP %d: smp_message_recv(): unknown msg %d\n",
 136                        smp_processor_id(), msg);
 137                 break;
 138         }
 139 }
 140
 141 static irqreturn_t call_function_action(int irq, void *data)
 142 {
 143         generic_smp_call_function_interrupt();
 144         return IRQ_HANDLED;
 145 }
 146
 147 static irqreturn_t reschedule_action(int irq, void *data)
 148 {
 149         /* we just need the return path side effect of checking need_resched */
 150         return IRQ_HANDLED;
 151 }
 152
 153 static irqreturn_t call_function_single_action(int irq, void *data)
 154 {
 155         generic_smp_call_function_single_interrupt();
 156         return IRQ_HANDLED;
 157 }
 158
 159 static irqreturn_t debug_ipi_action(int irq, void *data)
 160 {
 161         smp_message_recv(PPC_MSG_DEBUGGER_BREAK);
 162         return IRQ_HANDLED;
 163 }
 164
 165 static irq_handler_t smp_ipi_action[] = {
 166         [PPC_MSG_CALL_FUNCTION] =  call_function_action,
 167         [PPC_MSG_RESCHEDULE] = reschedule_action,
 168         [PPC_MSG_CALL_FUNC_SINGLE] = call_function_single_action,
 169         [PPC_MSG_DEBUGGER_BREAK] = debug_ipi_action,
 170 };
 171
 172 const char *smp_ipi_name[] = {
 173         [PPC_MSG_CALL_FUNCTION] =  "ipi call function",
 174         [PPC_MSG_RESCHEDULE] = "ipi reschedule",
 175         [PPC_MSG_CALL_FUNC_SINGLE] = "ipi call function single",
 176         [PPC_MSG_DEBUGGER_BREAK] = "ipi debugger",
 177 };
 178
 179 /* optional function to request ipi, for controllers with >= 4 ipis */
 180 int smp_request_message_ipi(int virq, int msg)
 181 {
 182         int err;
 183
 184         if (msg < 0 || msg > PPC_MSG_DEBUGGER_BREAK) {
 185                 return -EINVAL;
 186         }
 187 #if !defined(CONFIG_DEBUGGER) && !defined(CONFIG_KEXEC)
 188         if (msg == PPC_MSG_DEBUGGER_BREAK) {
 189                 return 1;
 190         }
 191 #endif
 192         err = request_irq(virq, smp_ipi_action[msg], IRQF_DISABLED|IRQF_PERCPU,
 193                           smp_ipi_name[msg], 0);
 194         WARN(err < 0, "unable to request_irq %d for %s (rc %d)\n",
 195                 virq, smp_ipi_name[msg], err);
 196
 197         return err;
 198 }
 199
 200 void smp_send_reschedule(int cpu)
 201 {
 202         if (likely(smp_ops))
 203                 smp_ops->message_pass(cpu, PPC_MSG_RESCHEDULE);
 204 }
 205
 206 void arch_send_call_function_single_ipi(int cpu)
 207 {
 208         smp_ops->message_pass(cpu, PPC_MSG_CALL_FUNC_SINGLE);
 209 }
 210
 211 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 212 {
 213         unsigned int cpu;
 214
 215         for_each_cpu(cpu, mask)
 216                 smp_ops->message_pass(cpu, PPC_MSG_CALL_FUNCTION);
 217 }
 218
 219 #ifdef CONFIG_DEBUGGER
 220 void smp_send_debugger_break(int cpu)
 221 {
 222         if (likely(smp_ops))
 223                 smp_ops->message_pass(cpu, PPC_MSG_DEBUGGER_BREAK);
 224 }
 225 #endif
 226
 227 #ifdef CONFIG_KEXEC
 228 void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
 229 {
 230         crash_ipi_function_ptr = crash_ipi_callback;
 231         if (crash_ipi_callback && smp_ops) {
 232                 mb();
 233                 smp_ops->message_pass(MSG_ALL_BUT_SELF, PPC_MSG_DEBUGGER_BREAK);
 234         }
 235 }
 236 #endif
 237
 238 static void stop_this_cpu(void *dummy)
 239 {
 240         /* Remove this CPU */
 241         set_cpu_online(smp_processor_id(), false);
 242
 243         local_irq_disable();
 244         while (1)
 245                 ;
 246 }
 247
 248 void smp_send_stop(void)
 249 {
 250         smp_call_function(stop_this_cpu, NULL, 0);
 251 }
 252
 253 struct thread_info *current_set[NR_CPUS];
 254
 255 static void __devinit smp_store_cpu_info(int id)
 256 {
 257         per_cpu(cpu_pvr, id) = mfspr(SPRN_PVR);
 258 }
 259
 260 void __init smp_prepare_cpus(unsigned int max_cpus)
 261 {
 262         unsigned int cpu;
 263
 264         DBG("smp_prepare_cpus\n");
 265
 266         /*
 267          * setup_cpu may need to be called on the boot cpu. We havent
 268          * spun any cpus up but lets be paranoid.
 269          */
 270         BUG_ON(boot_cpuid != smp_processor_id());
 271
 272         /* Fixup boot cpu */
 273         smp_store_cpu_info(boot_cpuid);
 274         cpu_callin_map[boot_cpuid] = 1;
 275
 276         for_each_possible_cpu(cpu) {
 277                 zalloc_cpumask_var_node(&per_cpu(cpu_sibling_map, cpu),
 278                                         GFP_KERNEL, cpu_to_node(cpu));
 279                 zalloc_cpumask_var_node(&per_cpu(cpu_core_map, cpu),
 280                                         GFP_KERNEL, cpu_to_node(cpu));
 281         }
 282
 283         cpumask_set_cpu(boot_cpuid, cpu_sibling_mask(boot_cpuid));
 284         cpumask_set_cpu(boot_cpuid, cpu_core_mask(boot_cpuid));
 285
 286         if (smp_ops)
 287                 if (smp_ops->probe)
 288                         max_cpus = smp_ops->probe();
 289                 else
 290                         max_cpus = NR_CPUS;
 291         else
 292                 max_cpus = 1;
 293 }
 294
 295 void __devinit smp_prepare_boot_cpu(void)
 296 {
 297         BUG_ON(smp_processor_id() != boot_cpuid);
 298 #ifdef CONFIG_PPC64
 299         paca[boot_cpuid].__current = current;
 300 #endif
 301         current_set[boot_cpuid] = task_thread_info(current);
 302 }
 303
 304 #ifdef CONFIG_HOTPLUG_CPU
 305 /* State of each CPU during hotplug phases */
 306 static DEFINE_PER_CPU(int, cpu_state) = { 0 };
 307
 308 int generic_cpu_disable(void)
 309 {
 310         unsigned int cpu = smp_processor_id();
 311
 312         if (cpu == boot_cpuid)
 313                 return -EBUSY;
 314
 315         set_cpu_online(cpu, false);
 316 #ifdef CONFIG_PPC64
 317         vdso_data->processorCount--;
 318 #endif
 319         migrate_irqs();
 320         return 0;
 321 }
 322
 323 void generic_cpu_die(unsigned int cpu)
 324 {
 325         int i;
 326
 327         for (i = 0; i < 100; i++) {
 328                 smp_rmb();
 329                 if (per_cpu(cpu_state, cpu) == CPU_DEAD)
 330                         return;
 331                 msleep(100);
 332         }
 333         printk(KERN_ERR "CPU%d didn't die...\n", cpu);
 334 }
 335
 336 void generic_mach_cpu_die(void)
 337 {
 338         unsigned int cpu;
 339
 340         local_irq_disable();
 341         idle_task_exit();
 342         cpu = smp_processor_id();
 343         printk(KERN_DEBUG "CPU%d offline\n", cpu);
 344         __get_cpu_var(cpu_state) = CPU_DEAD;
 345         smp_wmb();
 346         while (__get_cpu_var(cpu_state) != CPU_UP_PREPARE)
 347                 cpu_relax();
 348 }
 349
 350 void generic_set_cpu_dead(unsigned int cpu)
 351 {
 352         per_cpu(cpu_state, cpu) = CPU_DEAD;
 353 }
 354 #endif
 355
 356 struct create_idle {
 357         struct work_struct work;
 358         struct task_struct *idle;
 359         struct completion done;
 360         int cpu;
 361 };
 362
 363 static void __cpuinit do_fork_idle(struct work_struct *work)
 364 {
 365         struct create_idle *c_idle =
 366                 container_of(work, struct create_idle, work);
 367
 368         c_idle->idle = fork_idle(c_idle->cpu);
 369         complete(&c_idle->done);
 370 }
 371
 372 static int __cpuinit create_idle(unsigned int cpu)
 373 {
 374         struct thread_info *ti;
 375         struct create_idle c_idle = {
 376                 .cpu    = cpu,
 377                 .done   = COMPLETION_INITIALIZER_ONSTACK(c_idle.done),
 378         };
 379         INIT_WORK_ONSTACK(&c_idle.work, do_fork_idle);
 380
 381         c_idle.idle = get_idle_for_cpu(cpu);
 382
 383         /* We can't use kernel_thread since we must avoid to
 384          * reschedule the child. We use a workqueue because
 385          * we want to fork from a kernel thread, not whatever
 386          * userspace process happens to be trying to online us.
 387          */
 388         if (!c_idle.idle) {
 389                 schedule_work(&c_idle.work);
 390                 wait_for_completion(&c_idle.done);
 391         } else
 392                 init_idle(c_idle.idle, cpu);
 393         if (IS_ERR(c_idle.idle)) {
 394                 pr_err("Failed fork for CPU %u: %li", cpu, PTR_ERR(c_idle.idle));
 395                 return PTR_ERR(c_idle.idle);
 396         }
 397         ti = task_thread_info(c_idle.idle);
 398
 399 #ifdef CONFIG_PPC64
 400         paca[cpu].__current = c_idle.idle;
 401         paca[cpu].kstack = (unsigned long)ti + THREAD_SIZE - STACK_FRAME_OVERHEAD;
 402 #endif
 403         ti->cpu = cpu;
 404         current_set[cpu] = ti;
 405
 406         return 0;
 407 }
 408
 409 int __cpuinit __cpu_up(unsigned int cpu)
 410 {
 411         int rc, c;
 412
 413         secondary_ti = current_set[cpu];
 414
 415         if (smp_ops == NULL ||
 416             (smp_ops->cpu_bootable && !smp_ops->cpu_bootable(cpu)))
 417                 return -EINVAL;
 418
 419         /* Make sure we have an idle thread */
 420         rc = create_idle(cpu);
 421         if (rc)
 422                 return rc;
 423
 424         /* Make sure callin-map entry is 0 (can be leftover a CPU
 425          * hotplug
 426          */
 427         cpu_callin_map[cpu] = 0;
 428
 429         /* The information for processor bringup must
 430          * be written out to main store before we release
 431          * the processor.
 432          */
 433         smp_mb();
 434
 435         /* wake up cpus */
 436         DBG("smp: kicking cpu %d\n", cpu);
 437         smp_ops->kick_cpu(cpu);
 438
 439         /*
 440          * wait to see if the cpu made a callin (is actually up).
 441          * use this value that I found through experimentation.
 442          * -- Cort
 443          */
 444         if (system_state < SYSTEM_RUNNING)
 445                 for (c = 50000; c && !cpu_callin_map[cpu]; c--)
 446                         udelay(100);
 447 #ifdef CONFIG_HOTPLUG_CPU
 448         else
 449                 /*
 450                  * CPUs can take much longer to come up in the
 451                  * hotplug case.  Wait five seconds.
 452                  */
 453                 for (c = 5000; c && !cpu_callin_map[cpu]; c--)
 454                         msleep(1);
 455 #endif
 456
 457         if (!cpu_callin_map[cpu]) {
 458                 printk(KERN_ERR "Processor %u is stuck.\n", cpu);
 459                 return -ENOENT;
 460         }
 461
 462         DBG("Processor %u found.\n", cpu);
 463
 464         if (smp_ops->give_timebase)
 465                 smp_ops->give_timebase();
 466
 467         /* Wait until cpu puts itself in the online map */
 468         while (!cpu_online(cpu))
 469                 cpu_relax();
 470
 471         return 0;
 472 }
 473
 474 /* Return the value of the reg property corresponding to the given
 475  * logical cpu.
 476  */
 477 int cpu_to_core_id(int cpu)
 478 {
 479         struct device_node *np;
 480         const int *reg;
 481         int id = -1;
 482
 483         np = of_get_cpu_node(cpu, NULL);
 484         if (!np)
 485                 goto out;
 486
 487         reg = of_get_property(np, "reg", NULL);
 488         if (!reg)
 489                 goto out;
 490
 491         id = *reg;
 492 out:
 493         of_node_put(np);
 494         return id;
 495 }
 496
 497 /* Helper routines for cpu to core mapping */
 498 int cpu_core_index_of_thread(int cpu)
 499 {
 500         return cpu >> threads_shift;
 501 }
 502 EXPORT_SYMBOL_GPL(cpu_core_index_of_thread);
 503
 504 int cpu_first_thread_of_core(int core)
 505 {
 506         return core << threads_shift;
 507 }
 508 EXPORT_SYMBOL_GPL(cpu_first_thread_of_core);
 509
 510 /* Must be called when no change can occur to cpu_present_map,
 511  * i.e. during cpu online or offline.
 512  */
 513 static struct device_node *cpu_to_l2cache(int cpu)
 514 {
 515         struct device_node *np;
 516         struct device_node *cache;
 517
 518         if (!cpu_present(cpu))
 519                 return NULL;
 520
 521         np = of_get_cpu_node(cpu, NULL);
 522         if (np == NULL)
 523                 return NULL;
 524
 525         cache = of_find_next_cache_node(np);
 526
 527         of_node_put(np);
 528
 529         return cache;
 530 }
 531
 532 /* Activate a secondary processor. */
 533 void __devinit start_secondary(void *unused)
 534 {
 535         unsigned int cpu = smp_processor_id();
 536         struct device_node *l2_cache;
 537         int i, base;
 538
 539         atomic_inc(&init_mm.mm_count);
 540         current->active_mm = &init_mm;
 541
 542         smp_store_cpu_info(cpu);
 543         set_dec(tb_ticks_per_jiffy);
 544         preempt_disable();
 545         cpu_callin_map[cpu] = 1;
 546
 547         if (smp_ops->setup_cpu)
 548                 smp_ops->setup_cpu(cpu);
 549         if (smp_ops->take_timebase)
 550                 smp_ops->take_timebase();
 551
 552         secondary_cpu_time_init();
 553
 554         ipi_call_lock();
 555         notify_cpu_starting(cpu);
 556         set_cpu_online(cpu, true);
 557         /* Update sibling maps */
 558         base = cpu_first_thread_sibling(cpu);
 559         for (i = 0; i < threads_per_core; i++) {
 560                 if (cpu_is_offline(base + i))
 561                         continue;
 562                 cpumask_set_cpu(cpu, cpu_sibling_mask(base + i));
 563                 cpumask_set_cpu(base + i, cpu_sibling_mask(cpu));
 564
 565                 /* cpu_core_map should be a superset of
 566                  * cpu_sibling_map even if we don't have cache
 567                  * information, so update the former here, too.
 568                  */
 569                 cpumask_set_cpu(cpu, cpu_core_mask(base + i));
 570                 cpumask_set_cpu(base + i, cpu_core_mask(cpu));
 571         }
 572         l2_cache = cpu_to_l2cache(cpu);
 573         for_each_online_cpu(i) {
 574                 struct device_node *np = cpu_to_l2cache(i);
 575                 if (!np)
 576                         continue;
 577                 if (np == l2_cache) {
 578                         cpumask_set_cpu(cpu, cpu_core_mask(i));
 579                         cpumask_set_cpu(i, cpu_core_mask(cpu));
 580                 }
 581                 of_node_put(np);
 582         }
 583         of_node_put(l2_cache);
 584         ipi_call_unlock();
 585
 586         local_irq_enable();
 587
 588         cpu_idle();
 589
 590         BUG();
 591 }
 592
 593 int setup_profiling_timer(unsigned int multiplier)
 594 {
 595         return 0;
 596 }
 597
 598 void __init smp_cpus_done(unsigned int max_cpus)
 599 {
 600         cpumask_var_t old_mask;
 601
 602         /* We want the setup_cpu() here to be called from CPU 0, but our
 603          * init thread may have been "borrowed" by another CPU in the meantime
 604          * se we pin us down to CPU 0 for a short while
 605          */
 606         alloc_cpumask_var(&old_mask, GFP_NOWAIT);
 607         cpumask_copy(old_mask, &current->cpus_allowed);
 608         set_cpus_allowed_ptr(current, cpumask_of(boot_cpuid));
 609
 610         if (smp_ops && smp_ops->setup_cpu)
 611                 smp_ops->setup_cpu(boot_cpuid);
 612
 613         set_cpus_allowed_ptr(current, old_mask);
 614
 615         free_cpumask_var(old_mask);
 616
 617         if (smp_ops && smp_ops->bringup_done)
 618                 smp_ops->bringup_done();
 619
 620         dump_numa_cpu_topology();
 621
 622 }
 623
 624 int arch_sd_sibling_asym_packing(void)
 625 {
 626         if (cpu_has_feature(CPU_FTR_ASYM_SMT)) {
 627                 printk_once(KERN_INFO "Enabling Asymmetric SMT scheduling\n");
 628                 return SD_ASYM_PACKING;
 629         }
 630         return 0;
 631 }
 632
 633 #ifdef CONFIG_HOTPLUG_CPU
 634 int __cpu_disable(void)
 635 {
 636         struct device_node *l2_cache;
 637         int cpu = smp_processor_id();
 638         int base, i;
 639         int err;
 640
 641         if (!smp_ops->cpu_disable)
 642                 return -ENOSYS;
 643
 644         err = smp_ops->cpu_disable();
 645         if (err)
 646                 return err;
 647
 648         /* Update sibling maps */
 649         base = cpu_first_thread_sibling(cpu);
 650         for (i = 0; i < threads_per_core; i++) {
 651                 cpumask_clear_cpu(cpu, cpu_sibling_mask(base + i));
 652                 cpumask_clear_cpu(base + i, cpu_sibling_mask(cpu));
 653                 cpumask_clear_cpu(cpu, cpu_core_mask(base + i));
 654                 cpumask_clear_cpu(base + i, cpu_core_mask(cpu));
 655         }
 656
 657         l2_cache = cpu_to_l2cache(cpu);
 658         for_each_present_cpu(i) {
 659                 struct device_node *np = cpu_to_l2cache(i);
 660                 if (!np)
 661                         continue;
 662                 if (np == l2_cache) {
 663                         cpumask_clear_cpu(cpu, cpu_core_mask(i));
 664                         cpumask_clear_cpu(i, cpu_core_mask(cpu));
 665                 }
 666                 of_node_put(np);
 667         }
 668         of_node_put(l2_cache);
 669
 670
 671         return 0;
 672 }
 673
 674 void __cpu_die(unsigned int cpu)
 675 {
 676         if (smp_ops->cpu_die)
 677                 smp_ops->cpu_die(cpu);
 678 }
 679
 680 static DEFINE_MUTEX(powerpc_cpu_hotplug_driver_mutex);
 681
 682 void cpu_hotplug_driver_lock()
 683 {
 684         mutex_lock(&powerpc_cpu_hotplug_driver_mutex);
 685 }
 686
 687 void cpu_hotplug_driver_unlock()
 688 {
 689         mutex_unlock(&powerpc_cpu_hotplug_driver_mutex);
 690 }
 691
 692 void cpu_die(void)
 693 {
 694         if (ppc_md.cpu_die)
 695                 ppc_md.cpu_die();
 696
 697         /* If we return, we re-enter start_secondary */
 698         start_secondary_resume();
 699 }
 700
 701 #endif