kernel/power/smp.c

   1 /*
   2  * drivers/power/smp.c - Functions for stopping other CPUs.
   3  *
   4  * Copyright 2004 Pavel Machek <pavel@suse.cz>
   5  * Copyright (C) 2002-2003 Nigel Cunningham <ncunningham@clear.net.nz>
   6  *
   7  * This file is released under the GPLv2.
   8  */
   9
  10 #undef DEBUG
  11
  12 #include <linux/smp_lock.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/suspend.h>
  15 #include <linux/module.h>
  16 #include <asm/atomic.h>
  17 #include <asm/tlbflush.h>
  18
  19 static atomic_t cpu_counter, freeze;
  20
  21
  22 static void smp_pause(void * data)
  23 {
  24         struct saved_context ctxt;
  25         __save_processor_state(&ctxt);
  26         printk("Sleeping in:\n");
  27         dump_stack();
  28         atomic_inc(&cpu_counter);
  29         while (atomic_read(&freeze)) {
  30                 /* FIXME: restore takes place at random piece inside this.
  31                    This should probably be written in assembly, and
  32                    preserve general-purpose registers, too
  33
  34                    What about stack? We may need to move to new stack here.
  35
  36                    This should better be ran with interrupts disabled.
  37                  */
  38                 cpu_relax();
  39                 barrier();
  40         }
  41         atomic_dec(&cpu_counter);
  42         __restore_processor_state(&ctxt);
  43 }
  44
  45 static cpumask_t oldmask;
  46
  47 void disable_nonboot_cpus(void)
  48 {
  49         printk("Freezing CPUs (at %d)", smp_processor_id());
  50         oldmask = current->cpus_allowed;
  51         set_cpus_allowed(current, cpumask_of_cpu(0));
  52         current->state = TASK_INTERRUPTIBLE;
  53         schedule_timeout(HZ);
  54         printk("...");
  55         BUG_ON(smp_processor_id() != 0);
  56
  57         /* FIXME: for this to work, all the CPUs must be running
  58          * "idle" thread (or we deadlock). Is that guaranteed? */
  59
  60         atomic_set(&cpu_counter, 0);
  61         atomic_set(&freeze, 1);
  62         smp_call_function(smp_pause, NULL, 0, 0);
  63         while (atomic_read(&cpu_counter) < (num_online_cpus() - 1)) {
  64                 cpu_relax();
  65                 barrier();
  66         }
  67         printk("ok\n");
  68 }
  69
  70 void enable_nonboot_cpus(void)
  71 {
  72         printk("Restarting CPUs");
  73         atomic_set(&freeze, 0);
  74         while (atomic_read(&cpu_counter)) {
  75                 cpu_relax();
  76                 barrier();
  77         }
  78         printk("...");
  79         set_cpus_allowed(current, oldmask);
  80         schedule();
  81         printk("ok\n");
  82
  83 }
  84
  85