net: rps: fix cpu unplug (ac64da0b) · Commits · 戴 / test

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>

net/core/dev.c

+15 −5

Original line number	Diff line number	Diff line
		@@ -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);
		}

Admin message