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Subject[tip:sched/core] exit: Always reap resource stats in __exit_signal()
Commit-ID:  90ed9cbe765ad358b3151a12b8bf889a3cbcd573
Gitweb: http://git.kernel.org/tip/90ed9cbe765ad358b3151a12b8bf889a3cbcd573
Author: Rik van Riel <riel@redhat.com>
AuthorDate: Fri, 15 Aug 2014 16:05:36 -0400
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 8 Sep 2014 08:17:00 +0200

exit: Always reap resource stats in __exit_signal()

Oleg pointed out that wait_task_zombie adds a task's usage statistics
to the parent's signal struct, but the task's own signal struct should
also propagate the statistics at exit time.

This allows thread_group_cputime(reaped_zombie) to get the statistics
after __unhash_process() has made the task invisible to for_each_thread,
but before the thread has actually been rcu freed, making sure no
non-monotonic results are returned inside that window.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Guillaume Morin <guillaume@morinfr.org>
Cc: Ionut Alexa <ionut.m.alexa@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Michal Schmidt <mschmidt@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: umgwanakikbuti@gmail.com
Cc: fweisbec@gmail.com
Cc: srao@redhat.com
Cc: lwoodman@redhat.com
Cc: atheurer@redhat.com
Link: http://lkml.kernel.org/r/1408133138-22048-2-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/exit.c | 43 +++++++++++++++++++++----------------------
1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 32c58f7..b93d46d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -115,30 +115,29 @@ static void __exit_signal(struct task_struct *tsk)

if (tsk == sig->curr_target)
sig->curr_target = next_thread(tsk);
- /*
- * Accumulate here the counters for all threads but the
- * group leader as they die, so they can be added into
- * the process-wide totals when those are taken.
- * The group leader stays around as a zombie as long
- * as there are other threads. When it gets reaped,
- * the exit.c code will add its counts into these totals.
- * We won't ever get here for the group leader, since it
- * will have been the last reference on the signal_struct.
- */
- task_cputime(tsk, &utime, &stime);
- sig->utime += utime;
- sig->stime += stime;
- sig->gtime += task_gtime(tsk);
- sig->min_flt += tsk->min_flt;
- sig->maj_flt += tsk->maj_flt;
- sig->nvcsw += tsk->nvcsw;
- sig->nivcsw += tsk->nivcsw;
- sig->inblock += task_io_get_inblock(tsk);
- sig->oublock += task_io_get_oublock(tsk);
- task_io_accounting_add(&sig->ioac, &tsk->ioac);
- sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
}

+ /*
+ * Accumulate here the counters for all threads but the group leader
+ * as they die, so they can be added into the process-wide totals
+ * when those are taken. The group leader stays around as a zombie as
+ * long as there are other threads. When it gets reaped, the exit.c
+ * code will add its counts into these totals. We won't ever get here
+ * for the group leader, since it will have been the last reference on
+ * the signal_struct.
+ */
+ task_cputime(tsk, &utime, &stime);
+ sig->utime += utime;
+ sig->stime += stime;
+ sig->gtime += task_gtime(tsk);
+ sig->min_flt += tsk->min_flt;
+ sig->maj_flt += tsk->maj_flt;
+ sig->nvcsw += tsk->nvcsw;
+ sig->nivcsw += tsk->nivcsw;
+ sig->inblock += task_io_get_inblock(tsk);
+ sig->oublock += task_io_get_oublock(tsk);
+ task_io_accounting_add(&sig->ioac, &tsk->ioac);
+ sig->sum_sched_runtime += tsk->se.sum_exec_runtime;
sig->nr_threads--;
__unhash_process(tsk, group_dead);


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