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    SubjectRe: [Linux-IrDA]Re: [IrDA+SMP] Lockup in handle_IRQ_event

    > BTW: What i have seen in the ircomm_tty.c (2.2.18):
    > 647 save_flags(flags);
    > 648 cli();
    > 649
    > 650 skb = self->tx_skb;
    > 651 self->tx_skb = NULL;
    > 652
    > 653 restore_flags(flags);
    > and a lot of other places simply use "save_flags(flags); cli();
    > restore_flags()". Can someone enlighten me how this is supposed to work
    > on SMP machines ? AFAIK "cli()" only disables IRQs on the local
    > CPU so a different CPU could easily stumple half way as this
    > is definitly non atomic. Or is the tty layer protected by some
    > "big tty lock" ?

    On SMP __cli() disables interrupts on the local cpu, cli() also grabs
    the global irq lock which serialises irqs between cpus.

    Using a spinlock is much preferred if possible as grabbing the global
    irq lock is expensive (and in most cases unnecessary).

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      Last update: 2005-03-22 12:52    [W:0.038 / U:0.152 seconds]
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