Messages in this thread | | | Date | Mon, 21 Mar 2011 18:43:06 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 7/8] job control: Notify the real parent of job control events regardless of ptrace |
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On 03/08, Tejun Heo wrote: > > With recent changes, job control and ptrace stopped states are > properly separated and accessible to the real parent and the ptracer > respectively; however, notifications of job control stopped/continued > events to the real parent while ptraced are still missing.
Yes, great.
> /* > + * Test whether the target task of the usual cldstop notification - the > + * real_parent of the group_leader of @child - is the ptracer. > + */ > +static bool real_parent_is_ptracer(struct task_struct *child) > +{ > + return child->parent == child->group_leader->real_parent; > +}
Again, I am not sure we do not need same_thread_group(), but this is minor.
Hmm... in fact I can't convince myself we really need to look at child->group_leader, will recheck... Anyway, this is minor too.
> @@ -1757,7 +1768,20 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info) > spin_unlock_irq(¤t->sighand->siglock); > read_lock(&tasklist_lock); > if (may_ptrace_stop()) { > - do_notify_parent_cldstop(current, task_ptrace(current), why); > + /* > + * Notify parents of the stop. > + * > + * While ptraced, there are two parents - the ptracer and > + * the real_parent of the group_leader. The ptracer should > + * know about every stop while the real parent is only > + * interested in the completion of group stop. The states > + * for the two don't interact with each other. Notify > + * separately unless they're gonna be duplicates. > + */ > + do_notify_parent_cldstop(current, true, why); > + if (gstop_done && !real_parent_is_ptracer(current)) > + do_notify_parent_cldstop(current, false, why);
OK.
But what about "else" branch? If gstop_done == T but debugger has gone between spin_unlock(siglock) and read_lock(tasklist), we should do something.
ptrace_untrace() restores GROUP_STOP_PENDING in this case, so this task will stop again. But notification is lost.
Just in case, it is not that I blame this patch. Just I think we need a bit more changes here. Unless I missed something.
> @@ -2017,10 +2041,24 @@ relock: > > + /* > + * Notify the parent that we're continuing. This event is > + * always per-process and doesn't make whole lot of sense > + * for ptracers, who shouldn't consume the state via > + * wait(2) either, but, for backward compatibility, notify > + * the ptracer of the group leader too unless it's gonna be > + * a duplicate. > + */ > read_lock(&tasklist_lock); > + > + do_notify_parent_cldstop(current, false, why);
Nice,
> leader = current->group_leader; > + if (task_ptrace(leader) && !real_parent_is_ptracer(leader)) > + do_notify_parent_cldstop(leader, true, why);
Well, yes... This is ugly but compatible and documented, so I agree.
Oleg.
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