[tip:smp/hotplug] cpu/hotplug: Make target state writeable
From: tip-bot for Thomas Gleixner
Date: Tue Mar 01 2016 - 14:55:59 EST
Commit-ID: 757c989b9994f51b42d6be1bd33c7c12d16a3ac7
Gitweb: http://git.kernel.org/tip/757c989b9994f51b42d6be1bd33c7c12d16a3ac7
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Fri, 26 Feb 2016 18:43:32 +0000
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 1 Mar 2016 20:36:55 +0100
cpu/hotplug: Make target state writeable
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@xxxxxxxxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Rafael Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: "Srivatsa S. Bhat" <srivatsa@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Sebastian Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20160226182341.022814799@xxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
kernel/cpu.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++------
lib/Kconfig.debug | 13 ++++++++++
2 files changed, 78 insertions(+), 8 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 1979b89..be9335d 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -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) {
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8bfd1ac..f28f7fa 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -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