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>

2 files changed, 23 insertions, 9 deletions

diff --git a/include/linux/resource.h b/include/linux/resource.h
index ae13db714742..aaa423a6f3d9 100644
--- a/include/linux/resource.h
+++ b/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 */
diff --git a/kernel/sys.c b/kernel/sys.c
index f2a451366953..e423d0d9e6ff 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1545,6 +1545,19 @@ out:
  *
  */
 
+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);
 }