Messages in this thread Patch in this message |  | | Date | Mon, 9 Sep 2002 22:33:17 +0200 (CEST) | From | Ingo Molnar <> | Subject | Re: do_syslog/__down_trylock lockup in current BK |
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the attached patch fixes one bug in the way we did zap_thread() - but this alone does not fix the lockup.
the bug was that list_for_each_safe() is not 'safe enough' - zap_thread() drops the tasklist lock at which point anything might happen to the child list.
the lockup is likely in the while loop - ie. zap_thread() not actually reparenting a thread and thus causing an infinite loop - is that possible?
Ingo
--- linux/kernel/exit.c.orig Mon Sep 9 21:59:24 2002 +++ linux/kernel/exit.c Mon Sep 9 22:24:41 2002 @@ -493,7 +493,6 @@ static void exit_notify(void) { struct task_struct *t; - struct list_head *_p, *_n; forget_original_parent(current); /* @@ -554,17 +553,16 @@ do_notify_parent(current, current->exit_signal); zap_again: - list_for_each_safe(_p, _n, ¤t->children) - zap_thread(list_entry(_p,struct task_struct,sibling), current, 0); - list_for_each_safe(_p, _n, ¤t->ptrace_children) - zap_thread(list_entry(_p,struct task_struct,ptrace_list), current, 1); + while (!list_empty(¤t->children)) + zap_thread(list_entry(current->children.next,struct task_struct,sibling), current, 0); + while (!list_empty(¤t->ptrace_children)) + zap_thread(list_entry(current->ptrace_children.next,struct task_struct,sibling), current, 0); /* * zap_thread might drop the tasklist lock, thus we could * have new children queued back from the ptrace list into the * child list: */ - if (unlikely(!list_empty(¤t->children) || - !list_empty(¤t->ptrace_children))) + if (unlikely(!list_empty(¤t->children))) goto zap_again; /* * No need to unlock IRQs, we'll schedule() immediately - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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