Messages in this thread | | | Subject | Re: [PATCH] synchronize_irq needs a barrier | From | Benjamin Herrenschmidt <> | Date | Fri, 19 Oct 2007 14:58:30 +1000 |
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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 <herbert@gondor.apana.org.au>
Good for me.
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cheers, Ben.
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