On Fri, 2007-10-19 at 12:48 +0800, Herbert Xu wrote:
> [IRQ]: Fix synchronize_irq races with IRQ handler
>
> As it is some callers of synchronize_irq rely on memory barriers
> to provide synchronisation against the IRQ handlers. For example,
> the tg3 driver does
>
> tp->irq_sync = 1;
> smp_mb();
> synchronize_irq();
>
> and then in the IRQ handler:
>
> if (!tp->irq_sync)
> netif_rx_schedule(dev, &tp->napi);
>
> Unfortunately memory barriers only work well when they come in
> pairs. Because we don't actually have memory barriers on the
> IRQ path, the memory barrier before the synchronize_irq() doesn't
> actually protect us.
>
> In particular, synchronize_irq() may return followed by the
> result of netif_rx_schedule being made visible.
>
> This patch (mostly written by Linus) fixes this by using spin
> locks instead of memory barries on the synchronize_irq() path.
>
> Signed-off-by: Herbert Xu <[email protected]>
Good for me.
Acked-by: Benjamin Herrenschmidt <[email protected]>
Cheers,
Ben.
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