From patchwork Tue Jun 18 07:13:24 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: 13701886 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 DB669155CB9; Tue, 18 Jun 2024 07:25:36 +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=1718695538; cv=none; b=JrpEUMHdoXi+F3zx2gVx8kMOlANhVVik0emuocbgPSsZP26+Ny9bl2MQ86gx715MjCDjKhSJcvVPrw5r/CqRMBe1Jf1UwCbDE/8nPB5SpymrULHnTaTmgd94ZCtxwTdUG6g8VMFLC6SF8/pJljm16IHSJ9lSBvPsdtdnbZqIuBs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718695538; c=relaxed/simple; bh=uyor+YoAq5LCl1tympUAjuHINXAU0Rd4nLiZUnTuChE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XLM5VXwTkrjKFBsXqFEaG+U1aQjggcr1SSr0fASE3DRjtIKLNJfB0Qf+Ag7I4bSm87YiAFI9qLy7ATF8WYY6znAqq0wgutcGoFUvl7+qrMNMu/zQWEEARm1LW9PvcfJh/yLjitZRGY31lJ19O1B+Bx6H6P1FN5aBekhrdNJvwss= 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=CaSqNtTT; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=GuRcgJqX; 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="CaSqNtTT"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="GuRcgJqX" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1718695534; 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=MPqDekgBbaL2uHOA54ypCHD+Ebie1oWnMATs+QupYFo=; b=CaSqNtTTsxj+HcEAovoLcDE8oFpru83gnbQs16tLsSVFHz2rawWyZF9l0g4RMzYBRBoYqA K3pLtZ5NYLjwO11n7aCHYy2hX53FWTKOqHvsbDEBrx/XlctikUz4QIGLkINNubhPoJpFVS n46sw9G8WpGQjHMgw1CPnTd04UnALxVW1W/Yiouwfy1I0ORX4nR2h4+OGdR1vw18DWLdw2 oB9lC4vbF8AGCav0De1Ux1qTuLd5LCD7gZyMZWS4DaZeG6EkTAlwvE1kp/9ljX+liDX18k eOJF8Zn+bVjhG45Qpl0lm1cK0mb6ma2QwPbS+4fsiUzBmbHAcXWlt5/q/M4lWA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1718695534; 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=MPqDekgBbaL2uHOA54ypCHD+Ebie1oWnMATs+QupYFo=; b=GuRcgJqXopA9Gc1FKId2uTE5b3aGVQT2G2OZDA1gLSJZ2cKFhuacJqQ8SV94W01j6/aEx6 +tJv4EOCtr5Y7DAQ== 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 , Ben Segall , Daniel Bristot de Oliveira , Dietmar Eggemann , Juri Lelli , Mel Gorman , Steven Rostedt , Valentin Schneider , Vincent Guittot Subject: [PATCH v7 net-next 08/15] net: softnet_data: Make xmit per task. Date: Tue, 18 Jun 2024 09:13:24 +0200 Message-ID: <20240618072526.379909-9-bigeasy@linutronix.de> In-Reply-To: <20240618072526.379909-1-bigeasy@linutronix.de> References: <20240618072526.379909-1-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 Softirq is preemptible on PREEMPT_RT. Without a per-CPU lock in local_bh_disable() there is no guarantee that only one device is transmitting at a time. With preemption and multiple senders it is possible that the per-CPU `recursion' counter gets incremented by different threads and exceeds XMIT_RECURSION_LIMIT leading to a false positive recursion alert. The `more' member is subject to similar problems if set by one thread for one driver and wrongly used by another driver within another thread. Instead of adding a lock to protect the per-CPU variable it is simpler to make xmit per-task. Sending and receiving skbs happens always in thread context anyway. Having a lock to protected the per-CPU counter would block/ serialize two sending threads needlessly. It would also require a recursive lock to ensure that the owner can increment the counter further. Make the softnet_data.xmit a task_struct member on PREEMPT_RT. Add needed wrapper. Cc: Ben Segall Cc: Daniel Bristot de Oliveira Cc: Dietmar Eggemann Cc: Juri Lelli Cc: Mel Gorman Cc: Steven Rostedt Cc: Valentin Schneider Cc: Vincent Guittot Signed-off-by: Sebastian Andrzej Siewior --- include/linux/netdevice.h | 42 +++++++++++++++++++++++++--------- include/linux/netdevice_xmit.h | 13 +++++++++++ include/linux/sched.h | 5 +++- net/core/dev.c | 14 ++++++++++++ net/core/dev.h | 18 +++++++++++++++ 5 files changed, 80 insertions(+), 12 deletions(-) create mode 100644 include/linux/netdevice_xmit.h diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 85111502cf8f1..96b233a0bc2b3 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -43,6 +43,7 @@ #include #include +#include #include #include #include @@ -3223,13 +3224,7 @@ struct softnet_data { struct sk_buff_head xfrm_backlog; #endif /* written and read only by owning cpu: */ - struct { - u16 recursion; - u8 more; -#ifdef CONFIG_NET_EGRESS - u8 skip_txqueue; -#endif - } xmit; + struct netdev_xmit xmit; #ifdef CONFIG_RPS /* input_queue_head should be written by cpu owning this struct, * and only read by other cpus. Worth using a cache line. @@ -3257,10 +3252,18 @@ struct softnet_data { DECLARE_PER_CPU_ALIGNED(struct softnet_data, softnet_data); +#ifndef CONFIG_PREEMPT_RT static inline int dev_recursion_level(void) { return this_cpu_read(softnet_data.xmit.recursion); } +#else +static inline int dev_recursion_level(void) +{ + return current->net_xmit.recursion; +} + +#endif void __netif_schedule(struct Qdisc *q); void netif_schedule_queue(struct netdev_queue *txq); @@ -4875,18 +4878,35 @@ static inline ktime_t netdev_get_tstamp(struct net_device *dev, return hwtstamps->hwtstamp; } -static inline netdev_tx_t __netdev_start_xmit(const struct net_device_ops *ops, - struct sk_buff *skb, struct net_device *dev, - bool more) +#ifndef CONFIG_PREEMPT_RT +static inline void netdev_xmit_set_more(bool more) { __this_cpu_write(softnet_data.xmit.more, more); - return ops->ndo_start_xmit(skb, dev); } static inline bool netdev_xmit_more(void) { return __this_cpu_read(softnet_data.xmit.more); } +#else +static inline void netdev_xmit_set_more(bool more) +{ + current->net_xmit.more = more; +} + +static inline bool netdev_xmit_more(void) +{ + return current->net_xmit.more; +} +#endif + +static inline netdev_tx_t __netdev_start_xmit(const struct net_device_ops *ops, + struct sk_buff *skb, struct net_device *dev, + bool more) +{ + netdev_xmit_set_more(more); + return ops->ndo_start_xmit(skb, dev); +} static inline netdev_tx_t netdev_start_xmit(struct sk_buff *skb, struct net_device *dev, struct netdev_queue *txq, bool more) diff --git a/include/linux/netdevice_xmit.h b/include/linux/netdevice_xmit.h new file mode 100644 index 0000000000000..38325e0702968 --- /dev/null +++ b/include/linux/netdevice_xmit.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef _LINUX_NETDEVICE_XMIT_H +#define _LINUX_NETDEVICE_XMIT_H + +struct netdev_xmit { + u16 recursion; + u8 more; +#ifdef CONFIG_NET_EGRESS + u8 skip_txqueue; +#endif +}; + +#endif diff --git a/include/linux/sched.h b/include/linux/sched.h index 61591ac6eab6d..5187486c25222 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -36,6 +36,7 @@ #include #include #include +#include #include #include #include @@ -975,7 +976,9 @@ struct task_struct { /* delay due to memory thrashing */ unsigned in_thrashing:1; #endif - +#ifdef CONFIG_PREEMPT_RT + struct netdev_xmit net_xmit; +#endif unsigned long atomic_flags; /* Flags requiring atomic access. */ struct restart_block restart_block; diff --git a/net/core/dev.c b/net/core/dev.c index c361a7b69da86..c15b0215a66b7 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3940,6 +3940,7 @@ netdev_tx_queue_mapping(struct net_device *dev, struct sk_buff *skb) return netdev_get_tx_queue(dev, netdev_cap_txqueue(dev, qm)); } +#ifndef CONFIG_PREEMPT_RT static bool netdev_xmit_txqueue_skipped(void) { return __this_cpu_read(softnet_data.xmit.skip_txqueue); @@ -3950,6 +3951,19 @@ void netdev_xmit_skip_txqueue(bool skip) __this_cpu_write(softnet_data.xmit.skip_txqueue, skip); } EXPORT_SYMBOL_GPL(netdev_xmit_skip_txqueue); + +#else +static bool netdev_xmit_txqueue_skipped(void) +{ + return current->net_xmit.skip_txqueue; +} + +void netdev_xmit_skip_txqueue(bool skip) +{ + current->net_xmit.skip_txqueue = skip; +} +EXPORT_SYMBOL_GPL(netdev_xmit_skip_txqueue); +#endif #endif /* CONFIG_NET_EGRESS */ #ifdef CONFIG_NET_XGRESS diff --git a/net/core/dev.h b/net/core/dev.h index b7b518bc2be55..4984dd9b334bc 100644 --- a/net/core/dev.h +++ b/net/core/dev.h @@ -150,6 +150,8 @@ struct napi_struct *napi_by_id(unsigned int napi_id); void kick_defer_list_purge(struct softnet_data *sd, unsigned int cpu); #define XMIT_RECURSION_LIMIT 8 + +#ifndef CONFIG_PREEMPT_RT static inline bool dev_xmit_recursion(void) { return unlikely(__this_cpu_read(softnet_data.xmit.recursion) > @@ -165,5 +167,21 @@ static inline void dev_xmit_recursion_dec(void) { __this_cpu_dec(softnet_data.xmit.recursion); } +#else +static inline bool dev_xmit_recursion(void) +{ + return unlikely(current->net_xmit.recursion > XMIT_RECURSION_LIMIT); +} + +static inline void dev_xmit_recursion_inc(void) +{ + current->net_xmit.recursion++; +} + +static inline void dev_xmit_recursion_dec(void) +{ + current->net_xmit.recursion--; +} +#endif #endif