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Date: Mon, 20 Dec 2010 19:15:16 +0100 From: Oleg Nesterov <oleg@...hat.com> To: Tejun Heo <tj@...nel.org> Cc: roland@...hat.com, linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org, akpm@...ux-foundation.org, rjw@...k.pl, jan.kratochvil@...hat.com Subject: Re: [PATCH 13/16] ptrace: reorganize __ptrace_unlink() and ptrace_untrace() A bit off-topic note, On 12/06, Tejun Heo wrote: > > -static void ptrace_untrace(struct task_struct *child) > +void __ptrace_unlink(struct task_struct *child) > { > + struct signal_struct *sig = child->signal; > + > + BUG_ON(!child->ptrace); > + > spin_lock(&child->sighand->siglock); > + > if (task_is_traced(child)) { > /* > * If group stop is completed or in progress, it should > * participate in the group stop. Set GROUP_STOP_PENDING > * before kicking it. > */ > - if (child->signal->flags & SIGNAL_STOP_STOPPED || > - child->signal->group_stop_count) > + if (sig->flags & SIGNAL_STOP_STOPPED || sig->group_stop_count) > child->group_stop |= GROUP_STOP_PENDING; > signal_wake_up(child, 1); OK. Of course, I do not blame this patch, this mimics the current behaviour. But, afaics, this is not exactly right in the long term. Suppose that SIGNAL_STOP_STOPPED is set but the tracee is running (this can happen if, say, debugger resumes the tracee and exits). In this case, I think this thread should be stopped too. IIRC, I already tried to do this, but the patch (or idea) was nacked because it means another user-visible change. However, if we want to really fix things, we should fix this case too. If SIGNAL_STOP_STOPPED is set, there should be no running threads after detach. Or. We can change the rules for ptrace_resume(), more on this later. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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