kernel/smpboot.c

Source file repositories/reference/linux-study-clean/kernel/smpboot.c

File Facts

System
Linux kernel
Corpus path
kernel/smpboot.c
Extension
.c
Size
7384 bytes
Lines
323
Domain
Core OS
Bucket
Scheduler, Processes, Timers, Sync, And Syscalls
Inferred role
Core OS: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

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;

Annotation

Implementation Notes