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    SubjectRe: [1/1] connector/CBUS: new messaging subsystem. Revision number next.
    On 4/26/05, Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:
    > On Tue, 26 Apr 2005 13:20:08 -0500
    > Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:
    >
    > > On 4/26/05, Evgeniy Polyakov <johnpol@2ka.mipt.ru> wrote:
    > > > Yes, I found it too.
    > > > Following patch should be the solution:
    > > >
    > > > --- orig/drivers/connector/connector.c
    > > > +++ mod/drivers/connector/connector.c
    > > > @@ -146,13 +146,16 @@
    > > > spin_lock_bh(&dev->cbdev->queue_lock);
    > > > list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
    > > > if (cn_cb_equal(&__cbq->cb->id, &msg->id)) {
    > > > - __cbq->cb->priv = msg;
    > > > +
    > > > + if (!test_bit(0, &work->pending)) {
    > > > + __cbq->cb->priv = msg;
    > > >
    > > > - __cbq->ddata = data;
    > > > - __cbq->destruct_data = destruct_data;
    > > > + __cbq->ddata = data;
    > > > + __cbq->destruct_data = destruct_data;
    > > >
    > >
    > > Still not good enough - work->pending bit gets cleared when work has
    > > been scheduled, but before executing payload. You still have the race.
    >
    > Data pointer is copied before bit is set,
    > but I forget that it is not data, but another pointer
    > which may be overwritten.
    >
    > I think we may finish it by setting skb as data,
    > and call kfree_skb() as destructor.
    >

    Yes, that woudl work, although I would urge you to implement a message
    queue for callbacks (probably limit it to 1000 messages or so) to
    allow bursting.

    > Thank you for your analysis.

    You are welcome.

    --
    Dmitry
    -
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