path: root/kernel/posix-cpu-timers.c

/*
 * Implement CPU time clocks for the POSIX clock interface.
 */

#include <linux/sched.h>
#include <linux/posix-timers.h>
#include <linux/errno.h>
#include <linux/math64.h>
#include <asm/uaccess.h>
#include <linux/kernel_stat.h>

/*
 * Allocate the thread_group_cputime structure appropriately and fill in the
 * current values of the fields.  Called from copy_signal() via
 * thread_group_cputime_clone_thread() when adding a second or subsequent
 * thread to a thread group.  Assumes interrupts are enabled when called.
 */
int thread_group_cputime_alloc(struct task_struct *tsk)
{
	struct signal_struct *sig = tsk->signal;
	struct task_cputime *cputime;

	/*
	 * If we have multiple threads and we don't already have a
	 * per-CPU task_cputime struct (checked in the caller), allocate
	 * one and fill it in with the times accumulated so far.  We may
	 * race with another thread so recheck after we pick up the sighand
	 * lock.
	 */
	cputime = alloc_percpu(struct task_cputime);
	if (cputime == NULL)
		return -ENOMEM;
	spin_lock_irq(&tsk->sighand->siglock);
	if (sig->cputime.totals) {
		spin_unlock_irq(&tsk->sighand->siglock);
		free_percpu(cputime);
		return 0;
	}
	sig->cputime.totals = cputime;
	cputime = per_cpu_ptr(sig->cputime.totals, smp_processor_id());
	cputime->utime = tsk->utime;
	cputime->stime = tsk->stime;
	cputime->sum_exec_runtime = tsk->se.sum_exec_runtime;
	spin_unlock_irq(&tsk->sighand->siglock);
	return 0;
}

/**
 * thread_group_cputime - Sum the thread group time fields across all CPUs.
 *
 * @tsk:	The task we use to identify the thread group.
 * @times:	task_cputime structure in which we return the summed fields.
 *
 * Walk the list of CPUs to sum the per-CPU time fields in the thread group
 * time structure.
 */
void thread_group_cputime(
	struct task_struct *tsk,
	struct task_cputime *times)
{
	struct signal_struct *sig;
	int i;
	struct task_cputime *tot;

	sig = tsk->signal;
	if (unlikely(!sig) || !sig->cputime.totals) {
		times->utime = tsk->utime;
		times->stime = tsk->stime;
		times->sum_exec_runtime = tsk->se.sum_exec_runtime;
		return;
	}
	times->stime = times->utime = cputime_zero;
	times->sum_exec_runtime = 0;
	for_each_possible_cpu(i) {
		tot = per_cpu_ptr(tsk->signal->cputime.totals, i);
		times->utime = cputime_add(times->utime, tot-&