kernel/cpu.c: document clear_tasks_mm_cpumask()

#include <linux/oom.h>

#include <linux/rcupdate.h>

#include <linux/export.h>

#include <linux/bug.h>

#include <linux/kthread.h>

#include <linux/stop_machine.h>

#include <linux/mutex.h>

}

EXPORT_SYMBOL(unregister_cpu_notifier);

/**

 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU

 * @cpu: a CPU id

 *

 * This function walks all processes, finds a valid mm struct for each one and

 * then clears a corresponding bit in mm's cpumask.  While this all sounds

 * trivial, there are various non-obvious corner cases, which this function

 * tries to solve in a safe manner.

 *

 * Also note that the function uses a somewhat relaxed locking scheme, so it may

 * be called only for an already offlined CPU.

 */

void clear_tasks_mm_cpumask(int cpu)

{

	struct task_struct *p;

	 * Thus, we may use rcu_read_lock() here, instead of grabbing

	 * full-fledged tasklist_lock.

	 */

	WARN_ON(cpu_online(cpu));

	rcu_read_lock();

	for_each_process(p) {

		struct task_struct *t;

		/*

		 * Main thread might exit, but other threads may still have

		 * a valid mm. Find one.

		 */

		t = find_lock_task_mm(p);

		if (!t)

			continue;