From patchwork Wed Jun 12 16:44:36 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: 13695383 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 A658A18307D; Wed, 12 Jun 2024 17:03:24 +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=1718211806; cv=none; b=hUxf6Mwa6akOJDuS6N+ok2E+9QEo/NuLzg+GKoEEZc5Ng/MqjRtJJTNhOVXg+eMvLnQRNrNssgZ9Kw7/s8iY5UfcOnQa/cGzx+kzkJ+aOPrJn7rQ+4j680MSoMGDZ+eZX9ymQpLTwrQdjBy5A41YNJWa/JtqFnF99Cutd7O1JNE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718211806; c=relaxed/simple; bh=Dc9K7FbOzvnCnQ7YjwcHMDpDO+2CpuZPjAmDo/rJQPU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iVumuJOtsEF6nT/DEKe4OYhF7+PQ84FZI61B8ZMnRFXrxtfeM67av3dk0d12fyQTyMsHZXkLvgTLeaKqoONL1jU8JwgKBI4YuK3hjfiaVZGkSMdK5UZXlPmKh5ggBGIUX2Kfnj7IMCRN2Jp6t+irFKa7I1FMSYCXra7dYkDJHwM= 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=skoyXNOm; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=OB3owYzK; 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="skoyXNOm"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="OB3owYzK" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1718211798; 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=4rkxInydfFtfvggdcg//PVGon9qRuIuZC+F3Nel7lMs=; b=skoyXNOmo9GofkPsX77G+tnDRJKexu4QkvyvI5QT8jZuNa18/8Uw4QMNj1xW3ahmPF55M7 V8dWC+UjZXMI4lC/mSUTUhPM1HVbdmzDWakPilj5Poj2WVguuLeyggdNmE7EZ7q+DXIcfc aF272LJ54d2awxsQ2a7NO6sH1dhgRL4NTDYTfR0/OFX1DwWKxX0b0b3bKq2aGslQvOZvZz NrkP6QJ1ctKxiql9qcsnDUkI4ZVMxJh0+e9AWagTxDoAaNylKZph03wRdF/+y4O8D4aMzf UZTmtP1AkXumiZqNcMl+t7xEYJpMBkOkbrX+jaoK2BKUTua75YHJWZyyOgAFSQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1718211798; 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=4rkxInydfFtfvggdcg//PVGon9qRuIuZC+F3Nel7lMs=; b=OB3owYzKtLM152rdh7IJxd2PuPTOgkD6RYRpjtqGuEoyFluCrnZCK/cwW4ek7wm7WxPA0J HAPolJva868vqYCw== 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 v6 net-next 10/15] dev: Use nested-BH locking for softnet_data.process_queue. Date: Wed, 12 Jun 2024 18:44:36 +0200 Message-ID: <20240612170303.3896084-11-bigeasy@linutronix.de> In-Reply-To: <20240612170303.3896084-1-bigeasy@linutronix.de> References: <20240612170303.3896084-1-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 db6b6fc997e6d..ba406bc42b133 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. @@ -5935,6 +5937,7 @@ 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); @@ -5942,6 +5945,7 @@ 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(); } @@ -6063,7 +6067,9 @@ 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(); @@ -6072,7 +6078,9 @@ 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)) { @@ -6087,8 +6095,10 @@ 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); }