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    SubjectRe: [patch] proposed fix for ptrace() SMP race
    >>>>> On Sat, 8 Sep 2001 19:11:08 +0200, Andrea Arcangeli <andrea@suse.de> said:

    Andrea> On Fri, Sep 07, 2001 at 08:35:31AM -0700, David Mosberger
    Andrea> wrote:
    >> Also, other signals will still wake up the task. Yes, it won't
    >> get very far as do_signal() will notify the parent instead, but
    >> still, the task will run and that could be enough to create some
    >> race condition.

    Andrea> this is the real issue, agreed.

    Good.

    Andrea> However still I don't like the cpus_allowed racy approch. I
    Andrea> either prefer to force the deschedule with a new ptrace
    Andrea> bitflag with new hooks in the scheduler or with a blocker
    Andrea> (delayer) to the signals again with a new ptrace bitflag but
    Andrea> in this case with hooks in the signal code. I think putting
    Andrea> the hooks in the signal code is better.

    Yes, though I don't really see how you could do this without any
    change to the scheduler.

    Andrea> BTW, checking this stuff I found two bugs, one is the check
    Andrea> for cpus_allowed before calling reschedule_idle, such check
    Andrea> has to be removed, then it also seems the signals seems to
    Andrea> wakeup the task two times unless I've overlooked something.

    Andrea> You may want to make a new patch at the light of those
    Andrea> considerations otherwise I'll put this in my todo list once
    Andrea> more important things are solved.

    Why don't you keep it on your todo list. I too have a couple of other
    things I need to finish first so it will be a while before I'd get to
    this (not before November, I'd guess). But I'll keep it in mind as
    well.

    Thanks,

    --david
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