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netdevsim: call napi_schedule from a timer context

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The netdevsim driver was experiencing NOHZ tick-stop errors during packet
transmission due to pending softirq work when calling napi_schedule().
This issue was observed when running the netconsole selftest, which
triggered the following error message:

  NOHZ tick-stop error: local softirq work is pending, handler #08!!!

To fix this issue, introduce a timer that schedules napi_schedule()
from a timer context instead of calling it directly from the TX path.

Create an hrtimer for each queue and kick it from the TX path,
which then schedules napi_schedule() from the timer context.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250219-netdevsim-v3-1-811e2b8abc4c@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Breno Leitao 2025-02-19 08:41:20 -08:00 committed by Jakub Kicinski
parent 372ab5a5fe
commit bf3624cf1c
2 changed files with 21 additions and 1 deletions
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21
drivers/net/netdevsim/netdev.c
View File

@ -87,7 +87,8 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
if (unlikely(nsim_forward_skb(peer_dev, skb, rq) == NET_RX_DROP))
goto out_drop_cnt;
napi_schedule(&rq->napi);
if (!hrtimer_active(&rq->napi_timer))
hrtimer_start(&rq->napi_timer, us_to_ktime(5), HRTIMER_MODE_REL);
rcu_read_unlock();
u64_stats_update_begin(&ns->syncp);
@ -426,6 +427,22 @@ static int nsim_init_napi(struct netdevsim *ns)
return err;
}
static enum hrtimer_restart nsim_napi_schedule(struct hrtimer *timer)
{
struct nsim_rq *rq;
rq = container_of(timer, struct nsim_rq, napi_timer);
napi_schedule(&rq->napi);
return HRTIMER_NORESTART;
}
static void nsim_rq_timer_init(struct nsim_rq *rq)
{
hrtimer_init(&rq->napi_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
rq->napi_timer.function = nsim_napi_schedule;
}
static void nsim_enable_napi(struct netdevsim *ns)
{
struct net_device *dev = ns->netdev;
@ -615,11 +632,13 @@ static struct nsim_rq *nsim_queue_alloc(void)
return NULL;
skb_queue_head_init(&rq->skb_queue);
nsim_rq_timer_init(rq);
return rq;
}
static void nsim_queue_free(struct nsim_rq *rq)
{
hrtimer_cancel(&rq->napi_timer);
skb_queue_purge_reason(&rq->skb_queue, SKB_DROP_REASON_QUEUE_PURGE);
kfree(rq);
}

1
drivers/net/netdevsim/netdevsim.h
View File

@ -97,6 +97,7 @@ struct nsim_rq {
struct napi_struct napi;
struct sk_buff_head skb_queue;
struct page_pool *page_pool;
struct hrtimer napi_timer;
};
struct netdevsim {