summaryrefslogtreecommitdiffstats
path: root/kernel/smpboot.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/smpboot.c')
-rw-r--r--kernel/smpboot.c482
1 files changed, 482 insertions, 0 deletions
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
new file mode 100644
index 000000000..e4163042c
--- /dev/null
+++ b/kernel/smpboot.c
@@ -0,0 +1,482 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Common SMP CPU bringup/teardown functions
+ */
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/smp.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/sched/task.h>
+#include <linux/export.h>
+#include <linux/percpu.h>
+#include <linux/kthread.h>
+#include <linux/smpboot.h>
+
+#include "smpboot.h"
+
+#ifdef CONFIG_SMP
+
+#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
+/*
+ * For the hotplug case we keep the task structs around and reuse
+ * them.
+ */
+static DEFINE_PER_CPU(struct task_struct *, idle_threads);
+
+struct task_struct *idle_thread_get(unsigned int cpu)
+{
+ struct task_struct *tsk = per_cpu(idle_threads, cpu);
+
+ if (!tsk)
+ return ERR_PTR(-ENOMEM);
+ return tsk;
+}
+
+void __init idle_thread_set_boot_cpu(void)
+{
+ per_cpu(idle_threads, smp_processor_id()) = current;
+}
+
+/**
+ * idle_init - Initialize the idle thread for a cpu
+ * @cpu: The cpu for which the idle thread should be initialized
+ *
+ * Creates the thread if it does not exist.
+ */
+static inline void idle_init(unsigned int cpu)
+{
+ struct task_struct *tsk = per_cpu(idle_threads, cpu);
+
+ if (!tsk) {
+ tsk = fork_idle(cpu);
+ if (IS_ERR(tsk))
+ pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
+ else
+ per_cpu(idle_threads, cpu) = tsk;
+ }
+}
+
+/**
+ * idle_threads_init - Initialize idle threads for all cpus
+ */
+void __init idle_threads_init(void)
+{
+ unsigned int cpu, boot_cpu;
+
+ boot_cpu = smp_processor_id();
+
+ for_each_possible_cpu(cpu) {
+ if (cpu != boot_cpu)
+ idle_init(cpu);
+ }
+}
+#endif
+
+#endif /* #ifdef CONFIG_SMP */
+
+static LIST_HEAD(hotplug_threads);
+static DEFINE_MUTEX(smpboot_threads_lock);
+
+struct smpboot_thread_data {
+ unsigned int cpu;
+ unsigned int status;
+ struct smp_hotplug_thread *ht;
+};
+
+enum {
+ HP_THREAD_NONE = 0,
+ HP_THREAD_ACTIVE,
+ HP_THREAD_PARKED,
+};
+
+/**
+ * smpboot_thread_fn - percpu hotplug thread loop function
+ * @data: thread data pointer
+ *
+ * Checks for thread stop and park conditions. Calls the necessary
+ * setup, cleanup, park and unpark functions for the registered
+ * thread.
+ *
+ * Returns 1 when the thread should exit, 0 otherwise.
+ */
+static int smpboot_thread_fn(void *data)
+{
+ struct smpboot_thread_data *td = data;
+ struct smp_hotplug_thread *ht = td->ht;
+
+ while (1) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ preempt_disable();
+ if (kthread_should_stop()) {
+ __set_current_state(TASK_RUNNING);
+ preempt_enable();
+ /* cleanup must mirror setup */
+ if (ht->cleanup && td->status != HP_THREAD_NONE)
+ ht->cleanup(td->cpu, cpu_online(td->cpu));
+ kfree(td);
+ return 0;
+ }
+
+ if (kthread_should_park()) {
+ __set_current_state(TASK_RUNNING);
+ preempt_enable();
+ if (ht->park && td->status == HP_THREAD_ACTIVE) {
+ BUG_ON(td->cpu != smp_processor_id());
+ ht->park(td->cpu);
+ td->status = HP_THREAD_PARKED;
+ }
+ kthread_parkme();
+ /* We might have been woken for stop */
+ continue;
+ }
+
+ BUG_ON(td->cpu != smp_processor_id());
+
+ /* Check for state change setup */
+ switch (td->status) {
+ case HP_THREAD_NONE:
+ __set_current_state(TASK_RUNNING);
+ preempt_enable();
+ if (ht->setup)
+ ht->setup(td->cpu);
+ td->status = HP_THREAD_ACTIVE;
+ continue;
+
+ case HP_THREAD_PARKED:
+ __set_current_state(TASK_RUNNING);
+ preempt_enable();
+ if (ht->unpark)
+ ht->unpark(td->cpu);
+ td->status = HP_THREAD_ACTIVE;
+ continue;
+ }
+
+ if (!ht->thread_should_run(td->cpu)) {
+ preempt_enable_no_resched();
+ schedule();
+ } else {
+ __set_current_state(TASK_RUNNING);
+ preempt_enable();
+ ht->thread_fn(td->cpu);
+ }
+ }
+}
+
+static int
+__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
+{
+ struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
+ struct smpboot_thread_data *td;
+
+ if (tsk)
+ return 0;
+
+ td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
+ if (!td)
+ return -ENOMEM;
+ td->cpu = cpu;
+ td->ht = ht;
+
+ tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
+ ht->thread_comm);
+ if (IS_ERR(tsk)) {
+ kfree(td);
+ return PTR_ERR(tsk);
+ }
+ kthread_set_per_cpu(tsk, cpu);
+ /*
+ * Park the thread so that it could start right on the CPU
+ * when it is available.
+ */
+ kthread_park(tsk);
+ get_task_struct(tsk);
+ *per_cpu_ptr(ht->store, cpu) = tsk;
+ if (ht->create) {
+ /*
+ * Make sure that the task has actually scheduled out
+ * into park position, before calling the create
+ * callback. At least the migration thread callback
+ * requires that the task is off the runqueue.
+ */
+ if (!wait_task_inactive(tsk, TASK_PARKED))
+ WARN_ON(1);
+ else
+ ht->create(cpu);
+ }
+ return 0;
+}
+
+int smpboot_create_threads(unsigned int cpu)
+{
+ struct smp_hotplug_thread *cur;
+ int ret = 0;
+
+ mutex_lock(&smpboot_threads_lock);
+ list_for_each_entry(cur, &hotplug_threads, list) {
+ ret = __smpboot_create_thread(cur, cpu);
+ if (ret)
+ break;
+ }
+ mutex_unlock(&smpboot_threads_lock);
+ return ret;
+}
+
+static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
+{
+ struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
+
+ if (!ht->selfparking)
+ kthread_unpark(tsk);
+}
+
+int smpboot_unpark_threads(unsigned int cpu)
+{
+ struct smp_hotplug_thread *cur;
+
+ mutex_lock(&smpboot_threads_lock);
+ list_for_each_entry(cur, &hotplug_threads, list)
+ smpboot_unpark_thread(cur, cpu);
+ mutex_unlock(&smpboot_threads_lock);
+ return 0;
+}
+
+static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
+{
+ struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
+
+ if (tsk && !ht->selfparking)
+ kthread_park(tsk);
+}
+
+int smpboot_park_threads(unsigned int cpu)
+{
+ struct smp_hotplug_thread *cur;
+
+ mutex_lock(&smpboot_threads_lock);
+ list_for_each_entry_reverse(cur, &hotplug_threads, list)
+ smpboot_park_thread(cur, cpu);
+ mutex_unlock(&smpboot_threads_lock);
+ return 0;
+}
+
+static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
+{
+ unsigned int cpu;
+
+ /* We need to destroy also the parked threads of offline cpus */
+ for_each_possible_cpu(cpu) {
+ struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
+
+ if (tsk) {
+ kthread_stop(tsk);
+ put_task_struct(tsk);
+ *per_cpu_ptr(ht->store, cpu) = NULL;
+ }
+ }
+}
+
+/**
+ * smpboot_register_percpu_thread - Register a per_cpu thread related
+ * to hotplug
+ * @plug_thread: Hotplug thread descriptor
+ *
+ * Creates and starts the threads on all online cpus.
+ */
+int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
+{
+ unsigned int cpu;
+ int ret = 0;
+
+ get_online_cpus();
+ mutex_lock(&smpboot_threads_lock);
+ for_each_online_cpu(cpu) {
+ ret = __smpboot_create_thread(plug_thread, cpu);
+ if (ret) {
+ smpboot_destroy_threads(plug_thread);
+ goto out;
+ }
+ smpboot_unpark_thread(plug_thread, cpu);
+ }
+ list_add(&plug_thread->list, &hotplug_threads);
+out:
+ mutex_unlock(&smpboot_threads_lock);
+ put_online_cpus();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
+
+/**
+ * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
+ * @plug_thread: Hotplug thread descriptor
+ *
+ * Stops all threads on all possible cpus.
+ */
+void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
+{
+ get_online_cpus();
+ mutex_lock(&smpboot_threads_lock);
+ list_del(&plug_thread->list);
+ smpboot_destroy_threads(plug_thread);
+ mutex_unlock(&smpboot_threads_lock);
+ put_online_cpus();
+}
+EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
+
+static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
+
+/*
+ * Called to poll specified CPU's state, for example, when waiting for
+ * a CPU to come online.
+ */
+int cpu_report_state(int cpu)
+{
+ return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
+}
+
+/*
+ * If CPU has died properly, set its state to CPU_UP_PREPARE and
+ * return success. Otherwise, return -EBUSY if the CPU died after
+ * cpu_wait_death() timed out. And yet otherwise again, return -EAGAIN
+ * if cpu_wait_death() timed out and the CPU still hasn't gotten around
+ * to dying. In the latter two cases, the CPU might not be set up
+ * properly, but it is up to the arch-specific code to decide.
+ * Finally, -EIO indicates an unanticipated problem.
+ *
+ * Note that it is permissible to omit this call entirely, as is
+ * done in architectures that do no CPU-hotplug error checking.
+ */
+int cpu_check_up_prepare(int cpu)
+{
+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
+ atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
+ return 0;
+ }
+
+ switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
+
+ case CPU_POST_DEAD:
+
+ /* The CPU died properly, so just start it up again. */
+ atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
+ return 0;
+
+ case CPU_DEAD_FROZEN:
+
+ /*
+ * Timeout during CPU death, so let caller know.
+ * The outgoing CPU completed its processing, but after
+ * cpu_wait_death() timed out and reported the error. The
+ * caller is free to proceed, in which case the state
+ * will be reset properly by cpu_set_state_online().
+ * Proceeding despite this -EBUSY return makes sense
+ * for systems where the outgoing CPUs take themselves
+ * offline, with no post-death manipulation required from
+ * a surviving CPU.
+ */
+ return -EBUSY;
+
+ case CPU_BROKEN:
+
+ /*
+ * The most likely reason we got here is that there was
+ * a timeout during CPU death, and the outgoing CPU never
+ * did complete its processing. This could happen on
+ * a virtualized system if the outgoing VCPU gets preempted
+ * for more than five seconds, and the user attempts to
+ * immediately online that same CPU. Trying again later
+ * might return -EBUSY above, hence -EAGAIN.
+ */
+ return -EAGAIN;
+
+ default:
+
+ /* Should not happen. Famous last words. */
+ return -EIO;
+ }
+}
+
+/*
+ * Mark the specified CPU online.
+ *
+ * Note that it is permissible to omit this call entirely, as is
+ * done in architectures that do no CPU-hotplug error checking.
+ */
+void cpu_set_state_online(int cpu)
+{
+ (void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Wait for the specified CPU to exit the idle loop and die.
+ */
+bool cpu_wait_death(unsigned int cpu, int seconds)
+{
+ int jf_left = seconds * HZ;
+ int oldstate;
+ bool ret = true;
+ int sleep_jf = 1;
+
+ might_sleep();
+
+ /* The outgoing CPU will normally get done quite quickly. */
+ if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
+ goto update_state;
+ udelay(5);
+
+ /* But if the outgoing CPU dawdles, wait increasingly long times. */
+ while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
+ schedule_timeout_uninterruptible(sleep_jf);
+ jf_left -= sleep_jf;
+ if (jf_left <= 0)
+ break;
+ sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
+ }
+update_state:
+ oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
+ if (oldstate == CPU_DEAD) {
+ /* Outgoing CPU died normally, update state. */
+ smp_mb(); /* atomic_read() before update. */
+ atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
+ } else {
+ /* Outgoing CPU still hasn't died, set state accordingly. */
+ if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
+ oldstate, CPU_BROKEN) != oldstate)
+ goto update_state;
+ ret = false;
+ }
+ return ret;
+}
+
+/*
+ * Called by the outgoing CPU to report its successful death. Return
+ * false if this report follows the surviving CPU's timing out.
+ *
+ * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
+ * timed out. This approach allows architectures to omit calls to
+ * cpu_check_up_prepare() and cpu_set_state_online() without defeating
+ * the next cpu_wait_death()'s polling loop.
+ */
+bool cpu_report_death(void)
+{
+ int oldstate;
+ int newstate;
+ int cpu = smp_processor_id();
+
+ do {
+ oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
+ if (oldstate != CPU_BROKEN)
+ newstate = CPU_DEAD;
+ else
+ newstate = CPU_DEAD_FROZEN;
+ } while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
+ oldstate, newstate) != oldstate);
+ return newstate == CPU_DEAD;
+}
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
generated by cgit v1.2.3 (git 2.39.1) at 2024-10-31 20:50:00 +0000