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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 20 Jan 2016 15:39:05 +0100
Subject: [PATCH 199/354] net: provide a way to delegate processing a softirq
to ksoftirqd
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=fb1f8d10fb922529f1cb373bc3d13996917e6c52
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 <bigeasy@linutronix.de>
---
include/linux/interrupt.h | 8 ++++++++
kernel/softirq.c | 21 +++++++++++++++++++++
net/core/dev.c | 2 +-
3 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index e1438fe66467..97d9ba26915e 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -518,6 +518,14 @@ 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 27a4bb2303d0..25bcf2f2714b 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -721,6 +721,27 @@ void __raise_softirq_irqoff(unsigned int nr)
wakeup_proper_softirq(nr);
}
+/*
+ * 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!
*/
diff --git a/net/core/dev.c b/net/core/dev.c
index 01f06514aed9..797f64ecc587 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6397,7 +6397,7 @@ static __latent_entropy 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);
out:
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