sched_exit() is called by release_task(). If the task auto-reaps itself
this call happens a bit too early (the task still uses cpu after that).
If the task goes to TASK_ZOMBIE this call is unpredictably delayed.
I think it is better to do sched_exit() right before the last schedule().
We can use read_lock_rcu() instead of write_lock(tasklist). In that case
it is possible that sched_exit() changes ->time_slice/->sleep_avg of the
already dead ->parent, but I think this is tolerable.
Signed-off-by: Oleg Nesterov <[email protected]>
--- 2.6.17-rc6/kernel/sched.c~MOVE 2006-06-23 04:48:48.000000000 +0400
+++ 2.6.17-rc6/kernel/sched.c 2006-06-23 06:46:57.000000000 +0400
@@ -1479,10 +1479,13 @@ void fastcall wake_up_new_task(task_t *p
*/
void fastcall sched_exit(task_t *p)
{
- task_t *parent = p->parent;
+ task_t *parent;
unsigned long flags;
runqueue_t *rq;
+ rcu_read_lock();
+ parent = p->real_parent;
+
/*
* If the child was a (relative-) CPU hog then decrease
* the sleep_avg of the parent as well.
@@ -1498,6 +1501,7 @@ void fastcall sched_exit(task_t *p)
(EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
(EXIT_WEIGHT + 1);
task_rq_unlock(rq, &flags);
+ rcu_read_unlock();
}
/**
--- 2.6.17-rc6/kernel/exit.c~MOVE 2006-06-18 06:10:26.000000000 +0400
+++ 2.6.17-rc6/kernel/exit.c 2006-06-23 05:45:42.000000000 +0400
@@ -170,7 +170,6 @@ repeat:
zap_leader = (leader->exit_signal == -1);
}
- sched_exit(p);
write_unlock_irq(&tasklist_lock);
spin_unlock(&p->proc_lock);
proc_pid_flush(proc_dentry);
@@ -940,6 +939,8 @@ fastcall NORET_TYPE void do_exit(long co
if (tsk->splice_pipe)
__free_pipe_info(tsk->splice_pipe);
+ sched_exit(tsk);
+
/* PF_DEAD causes final put_task_struct after we schedule. */
preempt_disable();
BUG_ON(tsk->flags & PF_DEAD);
-
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