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    SubjectRe: SMP races in proc with thread_struct
    Andreas Ferber wrote:
    > On Fri, May 04, 2001 at 10:46:43PM +1000, Keith Owens wrote:
    > > For a read only case, the only important
    > > thing is not to die, one occurrence of bad data is tolerable.
    > Strong NACK. The pages where the bad data comes from may in some cases
    > already be reclaimed for other data, probably something security
    > relevant, which should never ever be given even read access by an
    > unauthorized user. Even if this event may be a very rare case, one
    > single occurrence of this is one to much.

    Agreed. Worse, it is not readonly. The /proc code task_lock's the task
    struct, thus writing to it.

    I'll post a patch shortly once I've tested it. Worse case only if the
    task is exiting I sweep the tasklist looking for the parent to see if
    the parent is still valid. I am not verifying if it is the actual
    parent (it might be a new task allocated at the same spot). I could
    just report 0 (or 1) for the parent for any process that is exiting, but
    then you won't be able to see the ppid for zombies. Or is there another
    state I can look for? What I really need is PF_EXITED :).

    I am a little concerned also about mm, file, tty and sig fields. These
    appear to be NULLed in do_exit(), but I haven't tracked down tty and sig
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