From b336369c1e1ad88495895260a9068eb18bc48b6c Mon Sep 17 00:00:00 2001 From: Joshua Hoke Date: Mon, 25 Oct 2010 01:44:22 +0000 Subject: [PATCH] macb: Don't re-enable interrupts while in polling mode On a busy network, the macb driver could get stuck in the interrupt handler, quickly triggering the watchdog, due to a confluence of factors: 1. macb_poll re-enables interrupts unconditionally, even when it will be called again because it exhausted its rx budget 2. macb_interrupt only disables interrupts after scheduling macb_poll, but scheduling fails when macb_poll is already scheduled because it didn't call napi_complete 3. macb_interrupt loops until the interrupt status register is clear, which will never happen in this case if the driver doesn't disable the RX interrupt Since macb_interrupt runs in interrupt context, this effectively locks up the machine, triggering the hardware watchdog. This issue was readily reproducible on a flooded network with a modified 2.6.27.48 kernel. The same problem appears to still be in the 2.6.36-rc8 driver code, so I am submitting this patch against that version. I have not tested this version of the patch except to make sure the kernel compiles. Signed-off-by: Joshua Hoke Signed-off-by: David S. Miller --- drivers/net/macb.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-) diff --git a/drivers/net/macb.c b/drivers/net/macb.c index 4297f6e8c4bc..f69e73e2191e 100644 --- a/drivers/net/macb.c +++ b/drivers/net/macb.c @@ -515,14 +515,15 @@ static int macb_poll(struct napi_struct *napi, int budget) (unsigned long)status, budget); work_done = macb_rx(bp, budget); - if (work_done < budget) + if (work_done < budget) { napi_complete(napi); - /* - * We've done what we can to clean the buffers. Make sure we - * get notified when new packets arrive. - */ - macb_writel(bp, IER, MACB_RX_INT_FLAGS); + /* + * We've done what we can to clean the buffers. Make sure we + * get notified when new packets arrive. + */ + macb_writel(bp, IER, MACB_RX_INT_FLAGS); + } /* TODO: Handle errors */ @@ -550,12 +551,16 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id) } if (status & MACB_RX_INT_FLAGS) { + /* + * There's no point taking any more interrupts + * until we have processed the buffers. The + * scheduling call may fail if the poll routine + * is already scheduled, so disable interrupts + * now. + */ + macb_writel(bp, IDR, MACB_RX_INT_FLAGS); + if (napi_schedule_prep(&bp->napi)) { - /* - * There's no point taking any more interrupts - * until we have processed the buffers - */ - macb_writel(bp, IDR, MACB_RX_INT_FLAGS); dev_dbg(&bp->pdev->dev, "scheduling RX softirq\n"); __napi_schedule(&bp->napi); -- 2.30.2