fork: call complete_vfork_done() after clearing child_tid and flushing rss-counters

Child should wake up the parent from vfork() only after finishing all
operations with shared mm.  There is no sense in using
CLONE_CHILD_CLEARTID together with CLONE_VFORK, but it looks more accurate
now.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/fork.c b/kernel/fork.c
index 017fb23d5983dc8eca06220ae9d81e9e37e0a4b9..2254fbf23567c1e79d60556e4c970855337f8270 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -787,9 +787,6 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
        /* Get rid of any cached register state */
        deactivate_mm(tsk, mm);
 
-       if (tsk->vfork_done)
-               complete_vfork_done(tsk);
-
        /*
         * If we're exiting normally, clear a user-space tid field if
         * requested.  We leave this alone when dying by signal, to leave
@@ -810,6 +807,13 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
                }
                tsk->clear_child_tid = NULL;
        }
+
+       /*
+        * All done, finally we can wake up parent and return this mm to him.
+        * Also kthread_stop() uses this completion for synchronization.
+        */
+       if (tsk->vfork_done)
+               complete_vfork_done(tsk);
 }
 
 /*