From 264524d5e5195f6e0f099bee20253a22b651e272 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 6 Jun 2011 20:50:03 +0000 Subject: [PATCH] net: cpu offline cause napi stall Frank Blaschka reported : During heavy network load we turn off/on cpus. Sometimes this causes a stall on the network device. Digging into the dump I found out following: napi is scheduled but does not run. From the I/O buffers and the napi state I see napi/rx_softirq processing has stopped because the budget was reached. napi stays in the softnet_data poll_list and the rx_softirq was raised again. I assume at this time the cpu offline comes in, the rx softirq is raised/moved to another cpu but napi stays in the poll_list of the softnet_data of the now offline cpu. Reviewing dev_cpu_callback (net/core/dev.c) I did not find the poll_list is transfered to the new cpu. This patch is a straightforward implementation of Frank suggestion : Transfert poll_list and trigger NET_RX_SOFTIRQ on new cpu. Reported-by: Frank Blaschka Signed-off-by: Heiko Carstens Signed-off-by: Eric Dumazet Tested-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/dev.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index 1af6cb27f67a..a54c9f87ddbb 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6178,6 +6178,11 @@ static int dev_cpu_callback(struct notifier_block *nfb, oldsd->output_queue = NULL; oldsd->output_queue_tailp = &oldsd->output_queue; } + /* Append NAPI poll list from offline CPU. */ + if (!list_empty(&oldsd->poll_list)) { + list_splice_init(&oldsd->poll_list, &sd->poll_list); + raise_softirq_irqoff(NET_RX_SOFTIRQ); + } raise_softirq_irqoff(NET_TX_SOFTIRQ); local_irq_enable(); -- 2.20.1