diff options
Diffstat (limited to 'debian/patches-rt/0008-net-softnet_data-Make-xmit-per-task.patch')
| -rw-r--r-- | debian/patches-rt/0008-net-softnet_data-Make-xmit-per-task.patch | 227 |
1 files changed, 227 insertions, 0 deletions
diff --git a/debian/patches-rt/0008-net-softnet_data-Make-xmit-per-task.patch b/debian/patches-rt/0008-net-softnet_data-Make-xmit-per-task.patch new file mode 100644 index 0000000000..24ba5a1789 --- /dev/null +++ b/debian/patches-rt/0008-net-softnet_data-Make-xmit-per-task.patch @@ -0,0 +1,227 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Mon, 21 Aug 2023 11:47:40 +0200 +Subject: [PATCH 08/15] net: softnet_data: Make xmit per task. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz + +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 <bsegall@google.com> +Cc: Daniel Bristot de Oliveira <bristot@redhat.com> +Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> +Cc: Juri Lelli <juri.lelli@redhat.com> +Cc: Mel Gorman <mgorman@suse.de> +Cc: Steven Rostedt <rostedt@goodmis.org> +Cc: Valentin Schneider <vschneid@redhat.com> +Cc: Vincent Guittot <vincent.guittot@linaro.org> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + 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 + +--- a/include/linux/netdevice.h ++++ b/include/linux/netdevice.h +@@ -43,6 +43,7 @@ + + #include <linux/netdev_features.h> + #include <linux/neighbour.h> ++#include <linux/netdevice_xmit.h> + #include <uapi/linux/netdevice.h> + #include <uapi/linux/if_bonding.h> + #include <uapi/linux/pkt_cls.h> +@@ -3222,13 +3223,7 @@ 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. +@@ -3256,10 +3251,18 @@ 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); +@@ -4874,18 +4877,35 @@ static inline ktime_t netdev_get_tstamp( + 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) +--- /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 +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -36,6 +36,7 @@ + #include <linux/signal_types.h> + #include <linux/syscall_user_dispatch_types.h> + #include <linux/mm_types_task.h> ++#include <linux/netdevice_xmit.h> + #include <linux/task_io_accounting.h> + #include <linux/posix-timers_types.h> + #include <linux/restart_block.h> +@@ -981,7 +982,9 @@ 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; +--- a/net/core/dev.c ++++ b/net/core/dev.c +@@ -3940,6 +3940,7 @@ netdev_tx_queue_mapping(struct net_devic + 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 +--- a/net/core/dev.h ++++ b/net/core/dev.h +@@ -150,6 +150,8 @@ struct napi_struct *napi_by_id(unsigned + 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_de + { + __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 |