diff options
Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0009-net-Avoid-the-IPI-to-free-the.patch | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/debian/patches-rt/0009-net-Avoid-the-IPI-to-free-the.patch b/debian/patches-rt/0009-net-Avoid-the-IPI-to-free-the.patch new file mode 100644 index 000000000..1f6687796 --- /dev/null +++ b/debian/patches-rt/0009-net-Avoid-the-IPI-to-free-the.patch @@ -0,0 +1,125 @@ +From c910f301d71266e18f63407ec6c65d19ae90e779 Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Mon, 15 Aug 2022 17:29:50 +0200 +Subject: [PATCH 09/62] net: Avoid the IPI to free the +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.1/older/patches-6.1.69-rt21.tar.xz + +skb_attempt_defer_free() collects a skbs, which was allocated on a +remote CPU, on a per-CPU list. These skbs are either freed on that +remote CPU once the CPU enters NET_RX or an remote IPI function is +invoked in to raise the NET_RX softirq if a threshold of pending skb has +been exceeded. +This remote IPI can cause the wakeup of ksoftirqd on PREEMPT_RT if the +remote CPU idle was idle. This is undesired because once the ksoftirqd +is running it will acquire all pending softirqs and they will not be +executed as part of the threaded interrupt until ksoftird goes idle +again. + +To void all this, schedule the deferred clean up from a worker. + +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/netdevice.h | 4 ++++ + net/core/dev.c | 37 ++++++++++++++++++++++++++++--------- + net/core/skbuff.c | 7 ++++++- + 3 files changed, 38 insertions(+), 10 deletions(-) + +diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h +index 0373e0935990..55d698367883 100644 +--- a/include/linux/netdevice.h ++++ b/include/linux/netdevice.h +@@ -3169,7 +3169,11 @@ struct softnet_data { + int defer_count; + int defer_ipi_scheduled; + struct sk_buff *defer_list; ++#ifndef CONFIG_PREEMPT_RT + call_single_data_t defer_csd; ++#else ++ struct work_struct defer_work; ++#endif + }; + + static inline void input_queue_head_incr(struct softnet_data *sd) +diff --git a/net/core/dev.c b/net/core/dev.c +index 070039f9296c..a3caa23be3cf 100644 +--- a/net/core/dev.c ++++ b/net/core/dev.c +@@ -4618,15 +4618,6 @@ static void rps_trigger_softirq(void *data) + + #endif /* CONFIG_RPS */ + +-/* Called from hardirq (IPI) context */ +-static void trigger_rx_softirq(void *data) +-{ +- struct softnet_data *sd = data; +- +- __raise_softirq_irqoff(NET_RX_SOFTIRQ); +- smp_store_release(&sd->defer_ipi_scheduled, 0); +-} +- + /* + * Check if this softnet_data structure is another cpu one + * If yes, queue it to our IPI list and return 1 +@@ -6684,6 +6675,30 @@ static void skb_defer_free_flush(struct softnet_data *sd) + } + } + ++#ifndef CONFIG_PREEMPT_RT ++/* Called from hardirq (IPI) context */ ++static void trigger_rx_softirq(void *data) ++{ ++ struct softnet_data *sd = data; ++ ++ __raise_softirq_irqoff(NET_RX_SOFTIRQ); ++ smp_store_release(&sd->defer_ipi_scheduled, 0); ++} ++ ++#else ++ ++static void trigger_rx_softirq(struct work_struct *defer_work) ++{ ++ struct softnet_data *sd; ++ ++ sd = container_of(defer_work, struct softnet_data, defer_work); ++ smp_store_release(&sd->defer_ipi_scheduled, 0); ++ local_bh_disable(); ++ skb_defer_free_flush(sd); ++ local_bh_enable(); ++} ++#endif ++ + static __latent_entropy void net_rx_action(struct softirq_action *h) + { + struct softnet_data *sd = this_cpu_ptr(&softnet_data); +@@ -11435,7 +11450,11 @@ static int __init net_dev_init(void) + INIT_CSD(&sd->csd, rps_trigger_softirq, sd); + sd->cpu = i; + #endif ++#ifndef CONFIG_PREEMPT_RT + INIT_CSD(&sd->defer_csd, trigger_rx_softirq, sd); ++#else ++ INIT_WORK(&sd->defer_work, trigger_rx_softirq); ++#endif + spin_lock_init(&sd->defer_lock); + + init_gro_hash(&sd->backlog); +diff --git a/net/core/skbuff.c b/net/core/skbuff.c +index 73b1e0e53534..a457a3445469 100644 +--- a/net/core/skbuff.c ++++ b/net/core/skbuff.c +@@ -6680,6 +6680,11 @@ nodefer: __kfree_skb(skb); + /* Make sure to trigger NET_RX_SOFTIRQ on the remote CPU + * if we are unlucky enough (this seems very unlikely). + */ +- if (unlikely(kick) && !cmpxchg(&sd->defer_ipi_scheduled, 0, 1)) ++ if (unlikely(kick) && !cmpxchg(&sd->defer_ipi_scheduled, 0, 1)) { ++#ifndef CONFIG_PREEMPT_RT + smp_call_function_single_async(cpu, &sd->defer_csd); ++#else ++ schedule_work_on(cpu, &sd->defer_work); ++#endif ++ } + } +-- +2.43.0 + |