[PATCH] taskstats: fix sub-threads accounting

If there are no listeners, taskstats_exit_send() just returns because
taskstats_exit_alloc() didn't allocate *tidstats.  This is wrong, each
sub-thread should do fill_tgid_exit() on exit, otherwise its ->delays is
not recorded in ->signal->stats and lost.

Q: We don't send TASKSTATS_TYPE_AGGR_TGID when single-threaded process
exits.  Is it good?  How can the listener figure out that it was actually a
process exit, not sub-thread?

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Balbir Singh <balbir@in.ibm.com>
Acked-by: Shailabh Nagar <nagar@watson.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 7 deletions

diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 2039585ec5e1..f45c5e70773c 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -455,10 +455,9 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
         int is_thread_group;
         struct nlattr *na;
 
-        if (!family_registered || !tidstats)
+        if (!family_registered)
                 return;
 
-        rc = 0;
         /*
          * Size includes space for nested attributes
          */
@@ -466,8 +465,15 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
                 nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
 
         is_thread_group = (tsk->signal->stats != NULL);
-        if (is_thread_group)
-                size = 2 * size;        /* PID + STATS + TGID + STATS */
+        if (is_thread_group) {
+                /* PID + STATS + TGID + STATS */
+                size = 2 * size;
+                /* fill the tsk->signal->stats structure */
+                fill_tgid_exit(tsk);
+        }
+
+        if (!tidstats)
+                return;
 
         rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
         if (rc < 0)
@@ -487,11 +493,8 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
                 goto send;
 
         /*
-         * tsk has/had a thread group so fill the tsk->signal->stats structure
          * Doesn't matter if tsk is the leader or the last group member leaving
          */
-
-        fill_tgid_exit(tsk);
         if (!group_dead)
                 goto send;