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@xxxxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
include/linux/interrupt.h | 8 ++++++++
kernel/softirq.c | 13 +++++++++++++
net/core/dev.c | 2 +-
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 79a9622b5a38..655cee096aed 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -465,6 +465,14 @@ 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);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index f4c2e679a7d7..e83fffff38cf 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -641,6 +641,19 @@ void __raise_softirq_irqoff(unsigned int nr)
}
/*
+ * Same as __raise_softirq_irqoff() but will process them in ksoftirqd
+ */
+void __raise_softirq_irqoff_ksoft(unsigned int nr)
+{
+ if (WARN_ON_ONCE(!__this_cpu_read(ksoftirqd)))
+ return;
+ trace_softirq_raise(nr);
+ or_softirq_pending(1UL << nr);
+ __this_cpu_read(ksoftirqd)->softirqs_raised |= (1U << nr);
+ wakeup_softirqd();
+}
+
+/*
* This function must run with irqs disabled!
*/
void raise_softirq_irqoff(unsigned int nr)
diff --git a/net/core/dev.c b/net/core/dev.c
index f4475ccbc19b..13a55d0df151 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4955,7 +4955,7 @@ static void net_rx_action(struct softirq_action *h)
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);
}
--
2.7.0.rc3
--
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