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SubjectRe: [PATCH] remove BUG_ON(p->ptrace) in release_task()
On Mon, Sep 02, 2002 at 02:38:03AM +0900, OGAWA Hirofumi wrote:
> Hi,
>
> I think, BUG_ON(p->ptrace) will be called if the CLONE_DETACH process
> is traced. This patch removes BUG_ON(p->ptrace), and also removes
> BUG_ON(p->ptrace) workaround in sys_wait4().

The BUG_ON is correct, and that isn't a workaround - if the list is not
empty, then it will be garbage after the task struct is freed. Your
patch breaks tracing of normal processes again, because the ptrace_list
will not be empty.

It may be that the BUG_ON can be triggered for detached processes. In
that case a ptrace_unlink is necessary somewhere else.

>
> Please apply.
> --
> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>
> --- linux-2.5.33/kernel/exit.c~ 2002-09-02 01:02:07.000000000 +0900
> +++ linux-2.5.33/kernel/exit.c 2002-09-02 00:54:47.000000000 +0900
> @@ -66,8 +66,7 @@
> atomic_dec(&p->user->processes);
> security_ops->task_free_security(p);
> free_uid(p->user);
> - BUG_ON(p->ptrace || !list_empty(&p->ptrace_list) ||
> - !list_empty(&p->ptrace_children));
> + BUG_ON(!list_empty(&p->ptrace_list)||!list_empty(&p->ptrace_children));
> unhash_process(p);
>
> release_thread(p);
> @@ -717,14 +716,8 @@
> ptrace_unlink(p);
> do_notify_parent(p, SIGCHLD);
> write_unlock_irq(&tasklist_lock);
> - } else {
> - if (p->ptrace) {
> - write_lock_irq(&tasklist_lock);
> - ptrace_unlink(p);
> - write_unlock_irq(&tasklist_lock);
> - }
> + } else
> release_task(p);
> - }
> goto end_wait4;
> default:
> continue;
> -
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>

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer
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