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[PATCH] Disable CPU hotplug during suspend

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The current suspend code has to be run on one CPU, so we use the CPU
hotplug to take the non-boot CPUs offline on SMP machines.  However, we
should also make sure that these CPUs will not be enabled by someone else
after we have disabled them.

The functions disable_nonboot_cpus() and enable_nonboot_cpus() are moved to
kernel/cpu.c, because they now refer to some stuff in there that should
better be static.  Also it's better if disable_nonboot_cpus() returns an
error instead of panicking if something goes wrong, and
enable_nonboot_cpus() has no reason to panic(), because the CPUs may have
been enabled by the userland before it tries to take them online.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Rafael J. Wysocki 2006-09-25 23:32:48 -07:00 • committed by Linus Torvalds
parent e8eff5ac29
commit e3920fb42c
8 changed files with 146 additions and 105 deletions
Download patch file Download diff file Expand all files Collapse all files

140
kernel/cpu.c
View file

@ -21,6 +21,11 @@ static DEFINE_MUTEX(cpu_bitmask_lock);
static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
* Should always be manipulated under cpu_add_remove_lock
*/
static int cpu_hotplug_disabled;
#ifdef CONFIG_HOTPLUG_CPU
/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
@ -108,30 +113,25 @@ static int take_cpu_down(void *unused)
return 0;
}
int cpu_down(unsigned int cpu)
/* Requires cpu_add_remove_lock to be held */
static int _cpu_down(unsigned int cpu)
{
int err;
struct task_struct *p;
cpumask_t old_allowed, tmp;
mutex_lock(&cpu_add_remove_lock);
if (num_online_cpus() == 1) {
err = -EBUSY;
goto out;
}
if (num_online_cpus() == 1)
return -EBUSY;
if (!cpu_online(cpu)) {
err = -EINVAL;
goto out;
}
if (!cpu_online(cpu))
return -EINVAL;
err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
(void *)(long)cpu);
if (err == NOTIFY_BAD) {
printk("%s: attempt to take down CPU %u failed\n",
__FUNCTION__, cpu);
err = -EINVAL;
goto out;
return -EINVAL;
}
/* Ensure that we are not runnable on dying cpu */
@ -179,22 +179,32 @@ out_thread:
err = kthread_stop(p);
out_allowed:
set_cpus_allowed(current, old_allowed);
out:
return err;
}
int cpu_down(unsigned int cpu)
{
int err = 0;
mutex_lock(&cpu_add_remove_lock);
if (cpu_hotplug_disabled)
err = -EBUSY;
else
err = _cpu_down(cpu);
mutex_unlock(&cpu_add_remove_lock);
return err;
}
#endif /*CONFIG_HOTPLUG_CPU*/
int __devinit cpu_up(unsigned int cpu)
/* Requires cpu_add_remove_lock to be held */
static int __devinit _cpu_up(unsigned int cpu)
{
int ret;
void *hcpu = (void *)(long)cpu;
mutex_lock(&cpu_add_remove_lock);
if (cpu_online(cpu) || !cpu_present(cpu)) {
ret = -EINVAL;
goto out;
}
if (cpu_online(cpu) || !cpu_present(cpu))
return -EINVAL;
ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
if (ret == NOTIFY_BAD) {
@ -219,7 +229,95 @@ out_notify:
if (ret != 0)
blocking_notifier_call_chain(&cpu_chain,
CPU_UP_CANCELED, hcpu);
out:
mutex_unlock(&cpu_add_remove_lock);
return ret;
}
int __devinit cpu_up(unsigned int cpu)
{
int err = 0;
mutex_lock(&cpu_add_remove_lock);
if (cpu_hotplug_disabled)
err = -EBUSY;
else
err = _cpu_up(cpu);
mutex_unlock(&cpu_add_remove_lock);
return err;
}
#ifdef CONFIG_SUSPEND_SMP
static cpumask_t frozen_cpus;
int disable_nonboot_cpus(void)
{
int cpu, first_cpu, error;
mutex_lock(&cpu_add_remove_lock);
first_cpu = first_cpu(cpu_present_map);
if (!cpu_online(first_cpu)) {
error = _cpu_up(first_cpu);
if (error) {
printk(KERN_ERR "Could not bring CPU%d up.\n",
first_cpu);
goto out;
}
}
error = set_cpus_allowed(current, cpumask_of_cpu(first_cpu));
if (error) {
printk(KERN_ERR "Could not run on CPU%d\n", first_cpu);
goto out;
}
/* We take down all of the non-boot CPUs in one shot to avoid races
* with the userspace trying to use the CPU hotplug at the same time
*/
cpus_clear(frozen_cpus);
printk("Disabling non-boot CPUs ...\n");
for_each_online_cpu(cpu) {
if (cpu == first_cpu)
continue;
error = _cpu_down(cpu);
if (!error) {
cpu_set(cpu, frozen_cpus);
printk("CPU%d is down\n", cpu);
} else {
printk(KERN_ERR "Error taking CPU%d down: %d\n",
cpu, error);
break;
}
}
if (!error) {
BUG_ON(num_online_cpus() > 1);
/* Make sure the CPUs won't be enabled by someone else */
cpu_hotplug_disabled = 1;
} else {
printk(KERN_ERR "Non-boot CPUs are not disabled");
}
out:
mutex_unlock(&cpu_add_remove_lock);
return error;
}
void enable_nonboot_cpus(void)
{
int cpu, error;
/* Allow everyone to use the CPU hotplug again */
mutex_lock(&cpu_add_remove_lock);
cpu_hotplug_disabled = 0;
mutex_unlock(&cpu_add_remove_lock);
printk("Enabling non-boot CPUs ...\n");
for_each_cpu_mask(cpu, frozen_cpus) {
error = cpu_up(cpu);
if (!error) {
printk("CPU%d is up\n", cpu);
continue;
}
printk(KERN_WARNING "Error taking CPU%d up: %d\n",
cpu, error);
}
cpus_clear(frozen_cpus);
}
#endif