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Miller" , Eric Dumazet , Paolo Abeni , David Wei Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Breno Leitao X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3669; i=leitao@debian.org; h=from:subject:message-id; bh=yKqC4ySa0GGYhnBuRaIQj26Sn1XtOBOC8Lq+InnucGc=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBntgm9+9ihFOxpJunxmla1PEccV6PPjN00NryTu gIgTKW4VkaJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCZ7YJvQAKCRA1o5Of/Hh3 bVKWD/9T21B/9atgWB6NZk0JFfi2RVremJMU1SxLhO47kfINTQpGGqogCEjA20vDV1+fLpLRMSv J/fcApremB3mku5ylmWp/UzF6rhvQBOzlFdrvHvoAs5Fznuz+O3ps53K1ufTpbypWeHd1yRQ5mz zuaY4Kq69opDOYvtVdnRu9916PzfBi46sn9K9SYSBhwNhe7+I/yjnjBMMlXpuB8s5MhAbDp7++t aB/dVcv9/Za+TmLGnpVzhslBSVO4IFh6C/psaw9jAI4qpT8yMJ9cpCSE/Gvim3/aceUW/xZ88Pz N4zEvLqOBRrdvvF9Kyn2MVd8O0Qv79zCpUTukJKj6LXgaHC/I3z6SEZTIsT05o8Qm1qi0qD08Oj WTkOoRqTHaksX5f4LXt32wTAcBOlurmpyyGRnZUZwKPvnzCGSmZWR+VEOp7DH53QvX2M8YI8QfY 9+QFllWV+BTav6tOr9wn2fxKVSLfCCZiKHwzFdz/EEH8mv9MOK0f14LrGrtIWliO9ZJt2trN/qI syTWdccffzWeZC3DuLYwl8t3idZWeb17XxnlPW/5c1drsWYyvd3mcq+0ownjverzmXGq/N+fWbZ SM8c3k9aX+HM15DZb1S6sBK3P5KV7mak06Vh+lz1vcSPpCTh4JjMa5V5cqtZ/xykMz0gz2jLF08 OS+euky/tXsBIwA== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Patchwork-Delegate: kuba@kernel.org 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 Signed-off-by: Breno Leitao --- Changes in v3: - Move the timer initialization and cancel close to the queue allocation/free (Jakub) - Link to v2: https://lore.kernel.org/r/20250217-netdevsim-v2-1-fc7fe177b98f@debian.org Changes in v2: - The approach implemented in v1 will not work, given that ndo_start_xmit() can be called with interrupt disable, and calling local_bh_enable() inside that function has nasty side effected. Jakub suggested creating a timer and calling napi_schedule() from that timer. - Link to v1: https://lore.kernel.org/r/20250212-netdevsim-v1-1-20ece94daae8@debian.org --- drivers/net/netdevsim/netdev.c | 21 ++++++++++++++++++++- drivers/net/netdevsim/netdevsim.h | 1 + 2 files changed, 21 insertions(+), 1 deletion(-) --- base-commit: 0784d83df3bfc977c13252a0599be924f0afa68d change-id: 20250212-netdevsim-258d2d628175 Best regards, diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c index 9b394ddc5206a7a5ca5440341551aac50c43e20c..a41dc79e9c2e082367af156b10b61f04be8c41fb 100644 --- a/drivers/net/netdevsim/netdev.c +++ b/drivers/net/netdevsim/netdev.c @@ -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); } diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h index 96d54c08043d3a62b0731efd43bc6a313998bf01..e757f85ed8617bb13ed0bf0e367803e4ddbd8e95 100644 --- a/drivers/net/netdevsim/netdevsim.h +++ b/drivers/net/netdevsim/netdevsim.h @@ -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 {