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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 <psodagud@codeaurora.org> Reported-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Tom Herbert <therbert@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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parent
57d737c5e2
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ac64da0b83
1 changed files with 15 additions and 5 deletions
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@ -7072,10 +7072,20 @@ static int dev_cpu_callback(struct notifier_block *nfb,
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oldsd->output_queue = NULL;
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oldsd->output_queue_tailp = &oldsd->output_queue;
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}
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/* Append NAPI poll list from offline CPU. */
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if (!list_empty(&oldsd->poll_list)) {
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list_splice_init(&oldsd->poll_list, &sd->poll_list);
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raise_softirq_irqoff(NET_RX_SOFTIRQ);
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/* Append NAPI poll list from offline CPU, with one exception :
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* process_backlog() must be called by cpu owning percpu backlog.
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* We properly handle process_queue & input_pkt_queue later.
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*/
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while (!list_empty(&oldsd->poll_list)) {
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struct napi_struct *napi = list_first_entry(&oldsd->poll_list,
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struct napi_struct,
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poll_list);
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list_del_init(&napi->poll_list);
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if (napi->poll == process_backlog)
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napi->state = 0;
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else
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____napi_schedule(sd, napi);
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}
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raise_softirq_irqoff(NET_TX_SOFTIRQ);
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@ -7086,7 +7096,7 @@ static int dev_cpu_callback(struct notifier_block *nfb,
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netif_rx_internal(skb);
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input_queue_head_incr(oldsd);
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}
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while ((skb = __skb_dequeue(&oldsd->input_pkt_queue))) {
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while ((skb = skb_dequeue(&oldsd->input_pkt_queue))) {
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netif_rx_internal(skb);
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input_queue_head_incr(oldsd);
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}
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