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Date: Sat, 23 May 2009 11:24:28 +0200
From: Michael Buesch <mb@...sch.de>
To: David Dillow <dave@...dillows.org>
Cc: Michael Riepe <michael.riepe@...glemail.com>,
Francois Romieu <romieu@...zoreil.com>,
Rui Santos <rsantos@...popie.com>,
Michael Büker <m.bueker@...lin.de>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2.6.30-rc4] r8169: avoid losing MSI interrupts
On Saturday 23 May 2009 03:29:34 David Dillow wrote:
> The 8169 chip only generates MSI interrupts when all enabled event
> sources are quiescent and one or more sources transition to active. If
> not all of the active events are acknowledged, or a new event becomes
> active while the existing ones are cleared in the handler, we will not
> see a new interrupt.
>
> The current interrupt handler masks off the Rx and Tx events once the
> NAPI handler has been scheduled, which opens a race window in which we
> can get another Rx or Tx event and never ACK'ing it, stopping all
> activity until the link is reset (ifconfig down/up). Fix this by always
> ACK'ing all event sources, and loop in the handler until we have all
> sources quiescent.
>
> Signed-off-by: David Dillow <dave@...dillows.org>
Thanks a lot, Dave! This fixes the issue on my chip.
You can add my:
Tested-by: Michael Buesch <mb@...sch.de>
Here's a patch that cleanly applies to 2.6.29.4:
Index: linux-2.6.29/drivers/net/r8169.c
===================================================================
--- linux-2.6.29.orig/drivers/net/r8169.c 2009-05-23 11:06:22.000000000 +0200
+++ linux-2.6.29/drivers/net/r8169.c 2009-05-23 11:08:17.000000000 +0200
@@ -3554,54 +3554,64 @@
int handled = 0;
int status;
+ /* loop handling interrupts until we have no new ones or
+ * we hit a invalid/hotplug case.
+ */
status = RTL_R16(IntrStatus);
+ while (status && status != 0xffff) {
+ handled = 1;
- /* hotplug/major error/no more work/shared irq */
- if ((status == 0xffff) || !status)
- goto out;
-
- handled = 1;
+ /* Handle all of the error cases first. These will reset
+ * the chip, so just exit the loop.
+ */
+ if (unlikely(!netif_running(dev))) {
+ rtl8169_asic_down(ioaddr);
+ break;
+ }
- if (unlikely(!netif_running(dev))) {
- rtl8169_asic_down(ioaddr);
- goto out;
- }
+ /* Work around for rx fifo overflow */
+ if (unlikely(status & RxFIFOOver) &&
+ (tp->mac_version == RTL_GIGA_MAC_VER_11)) {
+ netif_stop_queue(dev);
+ rtl8169_tx_timeout(dev);
+ break;
+ }
- status &= tp->intr_mask;
- RTL_W16(IntrStatus,
- (status & RxFIFOOver) ? (status | RxOverflow) : status);
+ if (unlikely(status & SYSErr)) {
+ rtl8169_pcierr_interrupt(dev);
+ break;
+ }
- if (!(status & tp->intr_event))
- goto out;
+ if (status & LinkChg)
+ rtl8169_check_link_status(dev, tp, ioaddr);
- /* Work around for rx fifo overflow */
- if (unlikely(status & RxFIFOOver) &&
- (tp->mac_version == RTL_GIGA_MAC_VER_11)) {
- netif_stop_queue(dev);
- rtl8169_tx_timeout(dev);
- goto out;
- }
+ /* We need to see the lastest version of tp->intr_mask to
+ * avoid ignoring an MSI interrupt and having to wait for
+ * another event which may never come.
+ */
+ smp_rmb();
+ if (status & tp->intr_mask & tp->napi_event) {
+ RTL_W16(IntrMask, tp->intr_event & ~tp->napi_event);
+ tp->intr_mask = ~tp->napi_event;
+
+ if (likely(netif_rx_schedule_prep(&tp->napi)))
+ __netif_rx_schedule(&tp->napi);
+ else if (netif_msg_intr(tp)) {
+ printk(KERN_INFO "%s: interrupt %04x in poll\n",
+ dev->name, status);
+ }
+ }
- if (unlikely(status & SYSErr)) {
- rtl8169_pcierr_interrupt(dev);
- goto out;
+ /* We only get a new MSI interrupt when all active irq
+ * sources on the chip have been acknowledged. So, ack
+ * everything we've seen and check if new sources have become
+ * active to avoid blocking all interrupts from the chip.
+ */
+ RTL_W16(IntrStatus,
+ (status & RxFIFOOver) ? (status | RxOverflow) : status);
+ status = RTL_R16(IntrStatus);
}
- if (status & LinkChg)
- rtl8169_check_link_status(dev, tp, ioaddr);
-
- if (status & tp->napi_event) {
- RTL_W16(IntrMask, tp->intr_event & ~tp->napi_event);
- tp->intr_mask = ~tp->napi_event;
-
- if (likely(netif_rx_schedule_prep(&tp->napi)))
- __netif_rx_schedule(&tp->napi);
- else if (netif_msg_intr(tp)) {
- printk(KERN_INFO "%s: interrupt %04x in poll\n",
- dev->name, status);
- }
- }
-out:
return IRQ_RETVAL(handled);
}
@@ -3617,13 +3627,15 @@
if (work_done < budget) {
netif_rx_complete(napi);
- tp->intr_mask = 0xffff;
- /*
- * 20040426: the barrier is not strictly required but the
- * behavior of the irq handler could be less predictable
- * without it. Btw, the lack of flush for the posted pci
- * write is safe - FR
+
+ /* We need for force the visibility of tp->intr_mask
+ * for other CPUs, as we can loose an MSI interrupt
+ * and potentially wait for a retransmit timeout if we don't.
+ * The posted write to IntrMask is safe, as it will
+ * eventually make it to the chip and we won't loose anything
+ * until it does.
*/
+ tp->intr_mask = 0xffff;
smp_wmb();
RTL_W16(IntrMask, tp->intr_event);
}
--
Greetings, Michael.
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