Messages in this thread | | | Date | Sun, 28 Nov 2010 21:30:00 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 11/14] ptrace: make group stop notification reliable against ptrace |
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On 11/26, Tejun Heo wrote: > > Group stop notifications are unreliable if one or more tasks of the > task group are being ptraced. If a ptraced task ends up finishing a > group stop, the notification is sent to the ptracer and the real > parent never gets notified.
Yes. I do not even know if this is bug or not, but certainly I agree, this doesn't look very nice.
> if (likely(!task_ptrace(current))) { > + bool do_notify = false; > + > + if (sig->flags & SIGNAL_NOTIFY_STOP) { > + sig->flags &= ~SIGNAL_NOTIFY_STOP; > + do_notify = true; > + } > + > spin_unlock_irq(¤t->sighand->siglock); > > - if (notify) { > + if (do_notify) { > read_lock(&tasklist_lock); > - do_notify_parent_cldstop(current, notify); > + do_notify_parent_cldstop(current, CLD_STOPPED);
This can race with ptrace_attach() in between.
IOW, this notification can go to the new tracer anyway.
Oleg.
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