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    SubjectRe: [PATCH 2.5] fixes for airo.c
    On Mon July 21 2003 13:00, Javier Achirica wrote:
    > Daniel,
    > Thank you for your patch. Some comments about it:
    > - I'd rather fix whatever is broken in the current code than going back to
    > spinlocks, as they increase latency and reduce concurrency. In any case,
    > please check your code. I've seen a spinlock in the interrupt handler that
    > may lock the system.

    but we need to protect from interrupts while accessing the card and waiting for
    completion. semaphores don't protect you from that. spin_lock_irqsave does. the
    spin_lock in the interrupt handler is there to protect from interrupts from
    other processors in a SMP system (see Documentation/spinlocks.txt) and is btw.
    a no-op on UP. and semaphores are quite heavy....

    > - The fix for the transmit code you mention, is about fixing the returned
    > value in case of error? If not, please explain it to me as I don't see any
    > other changes.

    - return values
    - when to free the skb, when not
    - disabling the queues
    - netif_wake_queue called from the interrupt handler only (and on the right
    - i think the priv->xmit stuff and then the schedule_work is evil:
    if you return 0 from the dev->hard_start_xmit then the network layer assumes
    that the packet was kfree_skb()'ed (which does only frees the packet when the
    refcount drops to zero.) this is the cause for the keventd killing, for sure!

    if you return 0 you already kfree_skb()'ed the packet. and that's it.

    > - Where did you fix a buffer overflow?

    - for(s = &statr->beaconPeriod; s <= &statr->_reserved[9]; s++)
    + for(s = &statr->beaconPeriod; s <= &statr->_reserved1; s++)

    ...which you also fixed in your patchset. (which is harmless on little-endian
    machines and evil on big-endian machines)


    > I submitted to Jeff an updated version just before you sent your e-mail.
    > It incorporates most of your fixes expect for the possible loop-forever.
    > It's more stable that the one in the current kernel tree.
    > Javier Achirica
    > On Fri, 18 Jul 2003, Daniel Ritz wrote:
    > > in 2.4.20+ airo.c is broken and can even kill keventd. this patch fixes it:
    > > - sane locking with spinlocks and irqs disabled instead of the buggy locking
    > > with semaphores
    > > - fix transmit code
    > > - safer unload ordering of disable irq, unregister_netdev, kfree
    > > - fix possible loop-forever bug
    > > - fix a buffer overflow
    > >
    > > a kernel 2.4 version of the patch is tested by some people with good results.
    > > against 2.6.0-test1-bk. please apply.
    > >
    > >
    > > rgds
    > > -daniel

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