A lot of kernel threads parented to /sbin/init slow down do_wait() when
a non-detached (user-space) process exits. Change reparent_kthread() to
use init_task as a parent. Since init_task can't go away, we don't need
to put the caller on init_task.children list.
NOTE: pstree doesn't show kernel threads with this patch.
Signed-off-by: Oleg Nesterov <[email protected]>
--- 2.6.21-rc5/kernel/exit.c~3_SWAPPER 2007-04-10 21:59:41.000000000 +0400
+++ 2.6.21-rc5/kernel/exit.c 2007-04-10 22:25:25.000000000 +0400
@@ -255,11 +255,11 @@ static int has_stopped_jobs(struct pid *
}
/**
- * reparent_kthread - Reparent the calling kernel thread to the init task of the pid space that the thread belongs to.
+ * reparent_kthread - Reparent the calling kernel thread to swapper.
*
* If a kernel thread is launched as a result of a system call, or if
- * it ever exits, it should generally reparent itself to init so that
- * it is correctly cleaned up on exit.
+ * it ever exits, it should generally reparent itself so that it is
+ * correctly cleaned up on exit.
*
* The various task state such as scheduling policy and priority may have
* been inherited from a user process, so we reset them to sane values here.
@@ -272,9 +272,8 @@ void reparent_kthread(void)
ptrace_unlink(current);
remove_parent(current);
- current->parent = init_pid_ns.child_reaper;
+ current->parent = &init_task;
current->real_parent = current->parent;
- add_parent(current);
/* make the task auto-reap */
current->exit_signal = -1;
-
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