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authorOleg Nesterov <oleg@redhat.com>2009-12-17 15:27:15 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-17 15:45:31 -0800
commit9cd80bbb07fcd6d4d037fad4297496d3b132ac6b (patch)
tree322216d34b6d5ba2366f53ba0d677950c4cde766 /fs/exec.c
parent0f67b0b0392ccca98459bf40b36c0037793b5f71 (diff)
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do_wait() optimization: do not place sub-threads on task_struct->children list
Thanks to Roland who pointed out de_thread() issues. Currently we add sub-threads to ->real_parent->children list. This buys nothing but slows down do_wait(). With this patch ->children contains only main threads (group leaders). The only complication is that forget_original_parent() should iterate over sub-threads by hand, and de_thread() needs another list_replace() when it changes ->group_leader. Henceforth do_wait_thread() can never see task_detached() && !EXIT_DEAD tasks, we can remove this check (and we can unify do_wait_thread() and ptrace_do_wait()). This change can confuse the optimistic search in mm_update_next_owner(), but this is fixable and minor. Perhaps badness() and oom_kill_process() should be updated, but they should be fixed in any case. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Roland McGrath <roland@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Ratan Nalumasu <rnalumasu@gmail.com> Cc: Vitaly Mayatskikh <vmayatsk@redhat.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 623a5cc3076..77db9a97a77 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -826,7 +826,9 @@ static int de_thread(struct task_struct *tsk)
attach_pid(tsk, PIDTYPE_PID, task_pid(leader));
transfer_pid(leader, tsk, PIDTYPE_PGID);
transfer_pid(leader, tsk, PIDTYPE_SID);
+
list_replace_rcu(&leader->tasks, &tsk->tasks);
+ list_replace_init(&leader->sibling, &tsk->sibling);
tsk->group_leader = tsk;
leader->group_leader = tsk;