From 93276e45fe388a4b995a79b464414a600265255e Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 13 Nov 2011 17:17:09 +0100
Subject: [PATCH 093/184] softirq: Check preemption after reenabling interrupts

raise_softirq_irqoff() disables interrupts and wakes the softirq
daemon, but after reenabling interrupts there is no preemption check,
so the execution of the softirq thread might be delayed arbitrarily.

In principle we could add that check to local_irq_enable/restore, but
that's overkill as the rasie_softirq_irqoff() sections are the only
ones which show this behaviour.

Reported-by: Carsten Emde <cbe@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/preempt.h | 3 +++
 net/core/dev.c          | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 7a7890e976739..dc194f3567e75 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -224,8 +224,10 @@ do { \
 
 #ifndef CONFIG_PREEMPT_RT
 # define preempt_enable_no_resched() sched_preempt_enable_no_resched()
+# define preempt_check_resched_rt() barrier();
 #else
 # define preempt_enable_no_resched() preempt_enable()
+# define preempt_check_resched_rt() preempt_check_resched()
 #endif
 
 #define preemptible()	(preempt_count() == 0 && !irqs_disabled())
@@ -296,6 +298,7 @@ do { \
 #define preempt_disable_notrace()		barrier()
 #define preempt_enable_no_resched_notrace()	barrier()
 #define preempt_enable_notrace()		barrier()
+#define preempt_check_resched_rt()		barrier()
 #define preemptible()				0
 
 #endif /* CONFIG_PREEMPT_COUNT */
diff --git a/net/core/dev.c b/net/core/dev.c
index c3637eaa9e754..839112c5b657d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3110,6 +3110,7 @@ static void __netif_reschedule(struct Qdisc *q)
 	sd->output_queue_tailp = &q->next_sched;
 	raise_softirq_irqoff(NET_TX_SOFTIRQ);
 	local_irq_restore(flags);
+	preempt_check_resched_rt();
 }
 
 void __netif_schedule(struct Qdisc *q)
@@ -3172,6 +3173,7 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
 	__this_cpu_write(softnet_data.completion_queue, skb);
 	raise_softirq_irqoff(NET_TX_SOFTIRQ);
 	local_irq_restore(flags);
+	preempt_check_resched_rt();
 }
 EXPORT_SYMBOL(__dev_kfree_skb_irq);
 
@@ -4758,6 +4760,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
 	rps_unlock(sd);
 
 	local_irq_restore(flags);
+	preempt_check_resched_rt();
 
 	atomic_long_inc(&skb->dev->rx_dropped);
 	kfree_skb(skb);
@@ -6502,12 +6505,14 @@ static void net_rps_action_and_irq_enable(struct softnet_data *sd)
 		sd->rps_ipi_list = NULL;
 
 		local_irq_enable();
+		preempt_check_resched_rt();
 
 		/* Send pending IPI's to kick RPS processing on remote cpus. */
 		net_rps_send_ipi(remsd);
 	} else
 #endif
 		local_irq_enable();
+	preempt_check_resched_rt();
 }
 
 static bool sd_has_rps_ipi_waiting(struct softnet_data *sd)
@@ -6585,6 +6590,7 @@ void __napi_schedule(struct napi_struct *n)
 	local_irq_save(flags);
 	____napi_schedule(this_cpu_ptr(&softnet_data), n);
 	local_irq_restore(flags);
+	preempt_check_resched_rt();
 }
 EXPORT_SYMBOL(__napi_schedule);
 
@@ -11413,6 +11419,7 @@ static int dev_cpu_dead(unsigned int oldcpu)
 
 	raise_softirq_irqoff(NET_TX_SOFTIRQ);
 	local_irq_enable();
+	preempt_check_resched_rt();
 
 #ifdef CONFIG_RPS
 	remsd = oldsd->rps_ipi_list;
-- 
2.55.0

