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cpu/hotplug: Make target state writeable

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Make it possible to write a target state to the per cpu state file, so we can
switch between states.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.022814799@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2016-02-26 18:43:32 +00:00
parent 98f8cdce1d
commit 757c989b99
2 changed files with 78 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

73
kernel/cpu.c
View file

@ -48,12 +48,14 @@ static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
* @teardown: Teardown function of the step
* @skip_onerr: Do not invoke the functions on error rollback
* Will go away once the notifiers are gone
* @cant_stop: Bringup/teardown can't be stopped at this step
*/
struct cpuhp_step {
const char *name;
int (*startup)(unsigned int cpu);
int (*teardown)(unsigned int cpu);
bool skip_onerr;
bool cant_stop;
};
static DEFINE_MUTEX(cpuhp_state_mutex);
@ -558,7 +560,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
if (num_online_cpus() == 1)
return -EBUSY;
if (!cpu_online(cpu))
if (!cpu_present(cpu))
return -EINVAL;
cpu_hotplug_begin();
@ -683,16 +685,25 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
cpu_hotplug_begin();
if (cpu_online(cpu) || !cpu_present(cpu)) {
if (!cpu_present(cpu)) {
ret = -EINVAL;
goto out;
}
/* Let it fail before we try to bring the cpu up */
idle = idle_thread_get(cpu);
if (IS_ERR(idle)) {
ret = PTR_ERR(idle);
/*
* The caller of do_cpu_up might have raced with another
* caller. Ignore it for now.
*/
if (st->state >= target)
goto out;
if (st->state == CPUHP_OFFLINE) {
/* Let it fail before we try to bring the cpu up */
idle = idle_thread_get(cpu);
if (IS_ERR(idle)) {
ret = PTR_ERR(idle);
goto out;
}
}
cpuhp_tasks_frozen = tasks_frozen;
@ -909,27 +920,32 @@ static struct cpuhp_step cpuhp_bp_states[] = {
.name = "threads:create",
.startup = smpboot_create_threads,
.teardown = NULL,
.cant_stop = true,
},
[CPUHP_NOTIFY_PREPARE] = {
.name = "notify:prepare",
.startup = notify_prepare,
.teardown = notify_dead,
.skip_onerr = true,
.cant_stop = true,
},
[CPUHP_BRINGUP_CPU] = {
.name = "cpu:bringup",
.startup = bringup_cpu,
.teardown = NULL,
.cant_stop = true,
},
[CPUHP_TEARDOWN_CPU] = {
.name = "cpu:teardown",
.startup = NULL,
.teardown = takedown_cpu,
.cant_stop = true,
},
[CPUHP_NOTIFY_ONLINE] = {
.name = "notify:online",
.startup = notify_online,
.teardown = notify_down_prepare,
.cant_stop = true,
},
#endif
[CPUHP_ONLINE] = {
@ -947,6 +963,7 @@ static struct cpuhp_step cpuhp_ap_states[] = {
.startup = notify_starting,
.teardown = notify_dying,
.skip_onerr = true,
.cant_stop = true,
},
#endif
[CPUHP_ONLINE] = {
@ -979,6 +996,46 @@ static ssize_t show_cpuhp_state(struct device *dev,
}
static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
static ssize_t write_cpuhp_target(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
struct cpuhp_step *sp;
int target, ret;
ret = kstrtoint(buf, 10, &target);
if (ret)
return ret;
#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
return -EINVAL;
#else
if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
return -EINVAL;
#endif
ret = lock_device_hotplug_sysfs();
if (ret)
return ret;
mutex_lock(&cpuhp_state_mutex);
sp = cpuhp_get_step(target);
ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
mutex_unlock(&cpuhp_state_mutex);
if (ret)
return ret;
if (st->state < target)
ret = do_cpu_up(dev->id, target);
else
ret = do_cpu_down(dev->id, target);
unlock_device_hotplug();
return ret ? ret : count;
}
static ssize_t show_cpuhp_target(struct device *dev,
struct device_attribute *attr, char *buf)
{
@ -986,7 +1043,7 @@ static ssize_t show_cpuhp_target(struct device *dev,
return sprintf(buf, "%d\n", st->target);
}
static DEVICE_ATTR(target, 0444, show_cpuhp_target, NULL);
static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
static struct attribute *cpuhp_cpu_attrs[] = {
&dev_attr_state.attr,
@ -1007,7 +1064,7 @@ static ssize_t show_cpuhp_states(struct device *dev,
int i;
mutex_lock(&cpuhp_state_mutex);
for (i = 0; i <= CPUHP_ONLINE; i++) {
for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
struct cpuhp_step *sp = cpuhp_get_step(i);
if (sp->name) {

13
lib/Kconfig.debug
View file

@ -1442,6 +1442,19 @@ config DEBUG_BLOCK_EXT_DEVT
Say N if you are unsure.
config CPU_HOTPLUG_STATE_CONTROL
bool "Enable CPU hotplug state control"
depends on DEBUG_KERNEL
depends on HOTPLUG_CPU
default n
help
Allows to write steps between "offline" and "online" to the CPUs
sysfs target file so states can be stepped granular. This is a debug
option for now as the hotplug machinery cannot be stopped and
restarted at arbitrary points yet.
Say N if your are unsure.
config NOTIFIER_ERROR_INJECTION
tristate "Notifier error injection"
depends on DEBUG_KERNEL