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    SubjectRe: [PATCH 2.5.73] Signal stack fixes #1 introduce PF_SS_ACTIVE
    Linus Torvalds <> writes:

    > On Fri, 4 Jul 2003, Jörn Engel wrote:
    > >
    > > So some application has it's signal handler on the signal stack and
    > > instead of returning to the kernel, it detect where it left off before
    > > the signal, mangles the last two stack frames, and goes back directly?
    > Yeah, basically a lot of old threading stuff did the equivalent of
    > longjump by hand.
    > It is entirely possible that they do not do this out of signal handlers,
    > since that has its own set of problems anyway, and one of the reasons for
    > doing co-operative user level threading is to not need locking, and thus
    > you never want to do any thread switching asynchronously (eg from a signal
    > context).
    > So I'm not saying that your patch will necessarily break stuff, I'm just
    > pointing out that it was actually done the way it is done on purpose.

    I would have to double check but I am pretty certain dosemu does
    this when running dpmi applications. An alternative stack is setup
    for signals so we get a stack we can control, and if we want to
    return to dosemu instead of the dpmi application we must change the
    stack we return to.

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      Last update: 2005-03-22 13:46    [W:0.021 / U:0.588 seconds]
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