From patchwork Fri Dec 15 17:07:29 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13494691 X-Patchwork-Delegate: kuba@kernel.org Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FE3045BFF; Fri, 15 Dec 2023 17:10:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Z1v8qLCV"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="/c5A367j" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1702660235; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9YY938P41v7tgAkEsD/QoBSvsRcX+2kJhvYsQnrL6Aw=; b=Z1v8qLCV+RLJiu/rblvMSN7tDD7HRrKGxcYCmF6KGyzzTfhi6Q3gCjZ2PZbm0ZRBM/spAv ndtFcpvAwtAlsxq8x5U6GZitY00Ew6iA944vQ8aHBvXItZiqelQzXMTSwrjDPBOKuj8nkH 2iH46n9ufTFdXcQW8jctOXi+eYFnf0iYV5jmePGS2f2zJpj3RbKec60JnNyyiKiw6LeE+M RhEhBWk6qdox8FeyxSq+zREuIVlDQr0ndyST6W3yM0MMWWuDEub7tpHAKxhlVJSANoSltD axHeE592+spSZ/XKkMJkCk7lg4hnarGZb/7qz6bZV8m2T2NJ2VF00LLIcEw2/Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1702660235; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9YY938P41v7tgAkEsD/QoBSvsRcX+2kJhvYsQnrL6Aw=; b=/c5A367jYpvBJ4WRTOzeEQIOJO45jcSIQ5G1gX8QMVs1c5Ii4wETrzynloABIM3EJhrHB8 +pkzwyAzbFNjYMAQ== To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: "David S. Miller" , Boqun Feng , Daniel Borkmann , Eric Dumazet , Frederic Weisbecker , Ingo Molnar , Jakub Kicinski , Paolo Abeni , Peter Zijlstra , Thomas Gleixner , Waiman Long , Will Deacon , Sebastian Andrzej Siewior Subject: [PATCH net-next 10/24] dev: Use nested-BH locking for softnet_data.process_queue. Date: Fri, 15 Dec 2023 18:07:29 +0100 Message-ID: <20231215171020.687342-11-bigeasy@linutronix.de> In-Reply-To: <20231215171020.687342-1-bigeasy@linutronix.de> References: <20231215171020.687342-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org softnet_data::process_queue is a per-CPU variable and relies on disabled BH for its locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT this data structure requires explicit locking. Add a local_lock_t to softnet_data and use local_lock_nested_bh() for locking of process_queue. This change adds only lockdep coverage and does not alter the functional behaviour for !PREEMPT_RT. Signed-off-by: Sebastian Andrzej Siewior --- include/linux/netdevice.h | 1 + net/core/dev.c | 17 +++++++++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 06436695c3679..88e27d3c39da2 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3238,6 +3238,7 @@ static inline bool dev_has_header(const struct net_device *dev) struct softnet_data { struct list_head poll_list; struct sk_buff_head process_queue; + local_lock_t process_queue_bh_lock; /* stats */ unsigned int processed; diff --git a/net/core/dev.c b/net/core/dev.c index 09232080843ee..5a0f6da7b3ae5 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -440,7 +440,9 @@ static RAW_NOTIFIER_HEAD(netdev_chain); * queue in the local softnet handler. */ -DEFINE_PER_CPU_ALIGNED(struct softnet_data, softnet_data); +DEFINE_PER_CPU_ALIGNED(struct softnet_data, softnet_data) = { + .process_queue_bh_lock = INIT_LOCAL_LOCK(process_queue_bh_lock), +}; EXPORT_PER_CPU_SYMBOL(softnet_data); #ifdef CONFIG_LOCKDEP @@ -5838,6 +5840,7 @@ static void flush_backlog(struct work_struct *work) } rps_unlock_irq_enable(sd); + local_lock_nested_bh(&softnet_data.process_queue_bh_lock); skb_queue_walk_safe(&sd->process_queue, skb, tmp) { if (skb->dev->reg_state == NETREG_UNREGISTERING) { __skb_unlink(skb, &sd->process_queue); @@ -5845,6 +5848,7 @@ static void flush_backlog(struct work_struct *work) input_queue_head_incr(sd); } } + local_unlock_nested_bh(&softnet_data.process_queue_bh_lock); local_bh_enable(); } @@ -5966,15 +5970,22 @@ static int process_backlog(struct napi_struct *napi, int quota) while (again) { struct sk_buff *skb; + local_lock_nested_bh(&softnet_data.process_queue_bh_lock); while ((skb = __skb_dequeue(&sd->process_queue))) { + local_unlock_nested_bh(&softnet_data.process_queue_bh_lock); rcu_read_lock(); __netif_receive_skb(skb); rcu_read_unlock(); + + local_lock_nested_bh(&softnet_data.process_queue_bh_lock); input_queue_head_incr(sd); - if (++work >= quota) + if (++work >= quota) { + local_unlock_nested_bh(&softnet_data.process_queue_bh_lock); return work; + } } + local_unlock_nested_bh(&softnet_data.process_queue_bh_lock); rps_lock_irq_disable(sd); if (skb_queue_empty(&sd->input_pkt_queue)) { @@ -5989,8 +6000,10 @@ static int process_backlog(struct napi_struct *napi, int quota) napi->state = 0; again = false; } else { + local_lock_nested_bh(&softnet_data.process_queue_bh_lock); skb_queue_splice_tail_init(&sd->input_pkt_queue, &sd->process_queue); + local_unlock_nested_bh(&softnet_data.process_queue_bh_lock); } rps_unlock_irq_enable(sd); }