From: Sebastian Andrzej Siewior Date: Wed, 20 Jan 2016 15:39:05 +0100 Subject: net: provide a way to delegate processing a softirq to ksoftirqd Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.1-rt3.tar.xz If the NET_RX uses up all of his budget it moves the following NAPI invocations into the `ksoftirqd`. On -RT it does not do so. Instead it rises the NET_RX softirq in its current context again. In order to get closer to mainline's behaviour this patch provides __raise_softirq_irqoff_ksoft() which raises the softirq in the ksoftird. Cc: stable-rt@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior --- include/linux/interrupt.h | 8 ++++++++ kernel/softirq.c | 21 +++++++++++++++++++++ net/core/dev.c | 2 +- 3 files changed, 30 insertions(+), 1 deletion(-) --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -524,6 +524,14 @@ extern void thread_do_softirq(void); extern void open_softirq(int nr, void (*action)(struct softirq_action *)); extern void softirq_init(void); extern void __raise_softirq_irqoff(unsigned int nr); +#ifdef CONFIG_PREEMPT_RT_FULL +extern void __raise_softirq_irqoff_ksoft(unsigned int nr); +#else +static inline void __raise_softirq_irqoff_ksoft(unsigned int nr) +{ + __raise_softirq_irqoff(nr); +} +#endif extern void raise_softirq_irqoff(unsigned int nr); extern void raise_softirq(unsigned int nr); --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -694,6 +694,27 @@ void __raise_softirq_irqoff(unsigned int } /* + * Same as __raise_softirq_irqoff() but will process them in ksoftirqd + */ +void __raise_softirq_irqoff_ksoft(unsigned int nr) +{ + unsigned int mask; + + if (WARN_ON_ONCE(!__this_cpu_read(ksoftirqd) || + !__this_cpu_read(ktimer_softirqd))) + return; + mask = 1UL << nr; + + trace_softirq_raise(nr); + or_softirq_pending(mask); + if (mask & TIMER_SOFTIRQS) + __this_cpu_read(ktimer_softirqd)->softirqs_raised |= mask; + else + __this_cpu_read(ksoftirqd)->softirqs_raised |= mask; + wakeup_proper_softirq(nr); +} + +/* * This function must run with irqs disabled! */ void raise_softirq_irqoff(unsigned int nr) --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6354,7 +6354,7 @@ static __latent_entropy void net_rx_acti list_splice_tail(&repoll, &list); list_splice(&list, &sd->poll_list); if (!list_empty(&sd->poll_list)) - __raise_softirq_irqoff(NET_RX_SOFTIRQ); + __raise_softirq_irqoff_ksoft(NET_RX_SOFTIRQ); net_rps_action_and_irq_enable(sd); out: