From ac64da0b83d82abe62f78b3d0e21cca31aea24fa Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 15 Jan 2015 17:04:22 -0800 Subject: [PATCH] net: rps: fix cpu unplug softnet_data.input_pkt_queue is protected by a spinlock that we must hold when transferring packets from victim queue to an active one. This is because other cpus could still be trying to enqueue packets into victim queue. A second problem is that when we transfert the NAPI poll_list from victim to current cpu, we absolutely need to special case the percpu backlog, because we do not want to add complex locking to protect process_queue : Only owner cpu is allowed to manipulate it, unless cpu is offline. Based on initial patch from Prasad Sodagudi & Subash Abhinov Kasiviswanathan. This version is better because we do not slow down packet processing, only make migration safer. Reported-by: Prasad Sodagudi Reported-by: Subash Abhinov Kasiviswanathan Signed-off-by: Eric Dumazet Cc: Tom Herbert Signed-off-by: David S. Miller --- net/core/dev.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 683d493aa1bf..171420e75b03 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -7072,10 +7072,20 @@ 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); + /* Append NAPI poll list from offline CPU, with one exception : + * process_backlog() must be called by cpu owning percpu backlog. + * We properly handle process_queue & input_pkt_queue later. + */ + while (!list_empty(&oldsd->poll_list)) { + struct napi_struct *napi = list_first_entry(&oldsd->poll_list, + struct napi_struct, + poll_list); + + list_del_init(&napi->poll_list); + if (napi->poll == process_backlog) + napi->state = 0; + else + ____napi_schedule(sd, napi); } raise_softirq_irqoff(NET_TX_SOFTIRQ); @@ -7086,7 +7096,7 @@ static int dev_cpu_callback(struct notifier_block *nfb, netif_rx_internal(skb); input_queue_head_incr(oldsd); } - while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) { + while ((skb = skb_dequeue(&oldsd->input_pkt_queue))) { netif_rx_internal(skb); input_queue_head_incr(oldsd); } -- 2.30.2