From patchwork Tue Jun 4 15:24:16 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13685601 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 7F60B148836; Tue, 4 Jun 2024 15:44:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717515894; cv=none; b=M7T0h40YiPueMuUkf0TpjGvDql+wsN87g9Y2zq+2rLqDek3+vApPGTHoy4IjURQ0GnQktgCdLfYg1wNsDmvk79bSv8FXJNOIBwyPADrsL89I/+YcVZTDwsbXaJUFQVgdEd1IAvmRMPyLUoEYI0ygAlxxIRsbS4/WX4jLEXHy9zw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717515894; c=relaxed/simple; bh=VK/VABrYhjmW0ToZR4LYavotlwxdlAnOZi5bz3ErL1E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZkQe3QgfFRMUHX0bIROWi66nYJPIEYcwJ8gem7MCzwQohsP2oJyJ5Cm9efAvzWs8cMvRvjT+CGZQQJGYbxcla3jML3gnkjJoT+hUuymxp5KMNQ5F1d8tPokwQ4Jz/Wc0WCHc26y2EJYVRQFFNe7cdkcM9zWp3HhOqwcLDljLR1I= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=ZpCKXM+9; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=4YtD6Khv; arc=none smtp.client-ip=193.142.43.55 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="ZpCKXM+9"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="4YtD6Khv" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1717515890; 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=1SyotpPfu1hPZWK9CfxpEh2uU+7qkWGCiXkZRaOdpNQ=; b=ZpCKXM+9WrCGWEG0UAt+9PONHJdcg0GsmcvnLaWnq2D6VxYCCTOqd/48ZC1vVKFeuQeHKg np0idBDlPHgxs73T/iwhSbS56A592kBQAe7Hnsm/25OCjc50OwvVlIfhjyLizH+arB1m1Q R25nSY1OAFlUlvcIElfE8VJdCjVuITtEuSf0aNYyO3InLWwxOJryaz4cQbKia6SVfKzxZH zvhJaOg4GU08Jn2ndOBTJKBvWap2TMr7OWpBUU/zadJpJRnuS3le4NfLdXukI76PH6EmoY h3q6qym/4iQkJBfmnjZPCe7zNFzgb07pGYTjLBxcvRmsmB0XpIUsEdOo3DxOwQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1717515890; 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=1SyotpPfu1hPZWK9CfxpEh2uU+7qkWGCiXkZRaOdpNQ=; b=4YtD6KhvS4c5YIzvfkVmxYjmKqyiuzExJKddr4fjyjjxdn0gNRYRwjxifcMY8zOmiNcRc+ 3RJBfgWMHdoV0/Bg== To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: "David S. Miller" , Daniel Bristot de Oliveira , 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 v4 net-next 09/14] dev: Use nested-BH locking for softnet_data.process_queue. Date: Tue, 4 Jun 2024 17:24:16 +0200 Message-ID: <20240604154425.878636-10-bigeasy@linutronix.de> In-Reply-To: <20240604154425.878636-1-bigeasy@linutronix.de> References: <20240604154425.878636-1-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. softnet_data::input_queue_head can be updated lockless. This is fine because this value is only update CPU local by the local backlog_napi thread. 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 | 12 +++++++++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index b5ec072ec2430..f0ab89caf3cc2 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3200,6 +3200,7 @@ 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 a66e4e744bbb4..2c3f86c8cd176 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -449,7 +449,9 @@ 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); /* Page_pool has a lockless array/stack to alloc/recycle pages. @@ -5934,6 +5936,7 @@ static void flush_backlog(struct work_struct *work) } backlog_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); @@ -5941,6 +5944,7 @@ static void flush_backlog(struct work_struct *work) rps_input_queue_head_incr(sd); } } + local_unlock_nested_bh(&softnet_data.process_queue_bh_lock); local_bh_enable(); } @@ -6062,7 +6066,9 @@ 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(); @@ -6071,7 +6077,9 @@ static int process_backlog(struct napi_struct *napi, int quota) return work; } + local_lock_nested_bh(&softnet_data.process_queue_bh_lock); } + local_unlock_nested_bh(&softnet_data.process_queue_bh_lock); backlog_lock_irq_disable(sd); if (skb_queue_empty(&sd->input_pkt_queue)) { @@ -6086,8 +6094,10 @@ static int process_backlog(struct napi_struct *napi, int quota) napi->state &= NAPIF_STATE_THREADED; 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); } backlog_unlock_irq_enable(sd); }