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Date: Thu, 24 Jul 2014 16:28:35 +0800 From: Sonic Zhang <sonic.adi@...il.com> To: Francois Romieu <romieu@...zoreil.com> Cc: "David S. Miller" <davem@...emloft.net>, netdev <netdev@...r.kernel.org>, adi-buildroot-devel@...ts.sourceforge.net, Sonic Zhang <sonic.zhang@...log.com>, Eric Dumazet <eric.dumazet@...il.com>, David Laight <David.Laight@...lab.com> Subject: Re: [PATCH v7] bfin_mac: convert bfin Ethernet driver to NAPI framework Hi Francois, On Wed, Jul 23, 2014 at 6:16 AM, Francois Romieu <romieu@...zoreil.com> wrote: > Sonic Zhang <sonic.adi@...il.com> : > [...] >> diff --git a/drivers/net/ethernet/adi/bfin_mac.c b/drivers/net/ethernet/adi/bfin_mac.c >> index 7ae74d4..8924802 100644 >> --- a/drivers/net/ethernet/adi/bfin_mac.c >> +++ b/drivers/net/ethernet/adi/bfin_mac.c > [...] >> @@ -1302,41 +1303,53 @@ out: >> current_rx_ptr = current_rx_ptr->next; >> } >> >> +static int bfin_mac_poll(struct napi_struct *napi, int budget) >> +{ >> + int i = 0; >> + struct bfin_mac_local *lp = container_of(napi, >> + struct bfin_mac_local, >> + napi); >> + >> + while (current_rx_ptr->status.status_word != 0 && i < budget) { >> + bfin_mac_rx(lp, budget); >> + i++; >> + } >> + >> + if (i < budget) { >> + napi_complete(napi); >> + if (lp->rx_irq_disabled--) >> + if (!lp->rx_irq_disabled) >> + enable_irq(IRQ_MAC_RX); >> + } > [...] >> static irqreturn_t bfin_mac_interrupt(int irq, void *dev_id) >> { >> + struct bfin_mac_local *lp = netdev_priv(dev_id); >> + u32 status; >> + >> + status = bfin_read_DMA1_IRQ_STATUS(); >> + >> + bfin_write_DMA1_IRQ_STATUS(status | DMA_DONE | DMA_ERR); >> + if ((status & DMA_DONE) && napi_schedule_prep(&lp->napi)) { >> + if (!lp->rx_irq_disabled++) >> + disable_irq_nosync(IRQ_MAC_RX); >> + __napi_schedule(&lp->napi); > > If netpoll scavenges between napi_schedule_prep and lp->rx_irq_disabled++ > on a different CPU, bfin_mac_interrupt may later __napi_schedule while > already napi_completed in netpoll...bfin_mac_poll(): bfin_mac_poll won't > be run in net_rx_action and IRQ_MAC_RX will stay disabled. > > I don't know if something on the blackfin arch prevents the window to > widen and makes it moot. > > As the bfin_mac driver requests the single non shared IRQ_MAC_RX irq, > couldn't we instead: > > static irqreturn_t bfin_mac_interrupt(int irq, void *dev_id) > [...] > if (status & DMA_DONE) { > disable_irq_nosync(IRQ_MAC_RX); > /* Code won't return here until a scheduled poll enables irq. */ > set_bit(BFIN_IRQ_DISABLED, &lp->flags); > napi_schedule(&lp->napi); > } > > static int bfin_mac_poll(struct napi_struct *napi, int budget) > [...] > if (i < budget) { > napi_complete(napi); > if (test_and_clear_bit(BFIN_IRQ_DISABLED, &lp->flags)) > enable_irq(IRQ_MAC_RX); > } > > Comments ? Yes, you suggestion can make sure both the balanced operations of the MAC RX IRQ and the NAPI poll is always called with MAC RX IRQ disabled. I just tested your suggestion on Blackfin with and without netpoll loop. Both work well. Thanks, Sonic Zhang -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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