add RUSAGE_THREAD

Add the RUSAGE_THREAD option for the getrusage system call.  This is
essentially Roland's patch from http://lkml.org/lkml/2008/1/18/589, but the
line about RUSAGE_LWP line has been removed, as suggested by Ulrich and
Christoph.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/resource.h

@@ -19,6 +19,7 @@ struct task_struct;
 #define	RUSAGE_SELF	0
 #define	RUSAGE_CHILDREN	(-1)
 #define RUSAGE_BOTH	(-2)		/* sys_wait4() uses this */
+#define	RUSAGE_THREAD	1		/* only the calling thread */
 
 struct	rusage {
 	struct timeval ru_utime;	/* user time used */

kernel/sys.c

@@ -1545,6 +1545,19 @@ asmlinkage long sys_setrlimit(unsigned int resource, struct rlimit __user *rlim)
  *
  */
 
+static void accumulate_thread_rusage(struct task_struct *t, struct rusage *r,
+				     cputime_t *utimep, cputime_t *stimep)
+{
+	*utimep = cputime_add(*utimep, t->utime);
+	*stimep = cputime_add(*stimep, t->stime);
+	r->ru_nvcsw += t->nvcsw;
+	r->ru_nivcsw += t->nivcsw;
+	r->ru_minflt += t->min_flt;
+	r->ru_majflt += t->maj_flt;
+	r->ru_inblock += task_io_get_inblock(t);
+	r->ru_oublock += task_io_get_oublock(t);
+}
+
 static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
 {
 	struct task_struct *t;
@@ -1554,6 +1567,11 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
 	memset((char *) r, 0, sizeof *r);
 	utime = stime = cputime_zero;
 
+	if (who == RUSAGE_THREAD) {
+		accumulate_thread_rusage(p, r, &utime, &stime);
+		goto out;
+	}
+
 	rcu_read_lock();
 	if (!lock_task_sighand(p, &flags)) {
 		rcu_read_unlock();
@@ -1586,14 +1604,7 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
 			r->ru_oublock += p->signal->oublock;
 			t = p;
 			do {
-				utime = cputime_add(utime, t->utime);
-				stime = cputime_add(stime, t->stime);
-				r->ru_nvcsw += t->nvcsw;
-				r->ru_nivcsw += t->nivcsw;
-				r->ru_minflt += t->min_flt;
-				r->ru_majflt += t->maj_flt;
-				r->ru_inblock += task_io_get_inblock(t);
-				r->ru_oublock += task_io_get_oublock(t);
+				accumulate_thread_rusage(t, r, &utime, &stime);
 				t = next_thread(t);
 			} while (t != p);
 			break;
@@ -1605,6 +1616,7 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
 	unlock_task_sighand(p, &flags);
 	rcu_read_unlock();
 
+out:
 	cputime_to_timeval(utime, &r->ru_utime);
 	cputime_to_timeval(stime, &r->ru_stime);
 }
@@ -1618,7 +1630,8 @@ int getrusage(struct task_struct *p, int who, struct rusage __user *ru)
 
 asmlinkage long sys_getrusage(int who, struct rusage __user *ru)
 {
-	if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN)
+	if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN &&
+	    who != RUSAGE_THREAD)
 		return -EINVAL;
 	return getrusage(current, who, ru);
 }