lkml.org 
[lkml]   [2011]   [Mar]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 7/8] job control: Notify the real parent of job control events regardless of ptrace
    On Mon, Mar 21, 2011 at 06:43:06PM +0100, Oleg Nesterov wrote:
    > > + * 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.

    Yeah, same_thread_group() would be better.

    > Hmm... in fact I can't convince myself we really need to look at
    > child->group_leader, will recheck... Anyway, this is minor too.

    Care to elaborate?

    > > @@ -1757,7 +1768,20 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
    > > spin_unlock_irq(&current->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.

    You mean when may_ptrace_stop() fails, right? Yeah, we need
    notification in the else clause. Will add it.

    Thanks.

    --
    tejun


    \
     
     \ /
      Last update: 2011-03-22 09:07    [W:3.269 / U:0.080 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site