1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
|
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 13 Nov 2011 17:17:09 +0100
Subject: [PATCH 119/342] softirq: Check preemption after reenabling interrupts
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=2c36de62cf384d49f3a0f23f7502b17c1be03ceb
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>
---
block/blk-softirq.c | 3 +++
include/linux/preempt.h | 3 +++
lib/irq_poll.c | 5 +++++
net/core/dev.c | 7 +++++++
4 files changed, 18 insertions(+)
diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 15c1f5e12eb8..1628277885a1 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -53,6 +53,7 @@ static void trigger_softirq(void *data)
raise_softirq_irqoff(BLOCK_SOFTIRQ);
local_irq_restore(flags);
+ preempt_check_resched_rt();
}
/*
@@ -91,6 +92,7 @@ static int blk_softirq_cpu_dead(unsigned int cpu)
this_cpu_ptr(&blk_cpu_done));
raise_softirq_irqoff(BLOCK_SOFTIRQ);
local_irq_enable();
+ preempt_check_resched_rt();
return 0;
}
@@ -143,6 +145,7 @@ void __blk_complete_request(struct request *req)
goto do_local;
local_irq_restore(flags);
+ preempt_check_resched_rt();
}
EXPORT_SYMBOL(__blk_complete_request);
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index b7fe717eb1f4..9984f2b75b73 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -187,8 +187,10 @@ do { \
#ifdef CONFIG_PREEMPT_RT_BASE
# define preempt_enable_no_resched() sched_preempt_enable_no_resched()
+# define preempt_check_resched_rt() preempt_check_resched()
#else
# define preempt_enable_no_resched() preempt_enable()
+# define preempt_check_resched_rt() barrier();
#endif
#define preemptible() (preempt_count() == 0 && !irqs_disabled())
@@ -275,6 +277,7 @@ 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
#define migrate_disable() barrier()
diff --git a/lib/irq_poll.c b/lib/irq_poll.c
index 86a709954f5a..9c069ef83d6d 100644
--- a/lib/irq_poll.c
+++ b/lib/irq_poll.c
@@ -37,6 +37,7 @@ void irq_poll_sched(struct irq_poll *iop)
list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
local_irq_restore(flags);
+ preempt_check_resched_rt();
}
EXPORT_SYMBOL(irq_poll_sched);
@@ -72,6 +73,7 @@ void irq_poll_complete(struct irq_poll *iop)
local_irq_save(flags);
__irq_poll_complete(iop);
local_irq_restore(flags);
+ preempt_check_resched_rt();
}
EXPORT_SYMBOL(irq_poll_complete);
@@ -96,6 +98,7 @@ static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
}
local_irq_enable();
+ preempt_check_resched_rt();
/* Even though interrupts have been re-enabled, this
* access is safe because interrupts can only add new
@@ -133,6 +136,7 @@ static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
local_irq_enable();
+ preempt_check_resched_rt();
}
/**
@@ -196,6 +200,7 @@ static int irq_poll_cpu_dead(unsigned int cpu)
this_cpu_ptr(&blk_cpu_iopoll));
__raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
local_irq_enable();
+ preempt_check_resched_rt();
return 0;
}
diff --git a/net/core/dev.c b/net/core/dev.c
index 42f6ff8b9703..b8e3ae050bcc 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2725,6 +2725,7 @@ 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)
@@ -2787,6 +2788,7 @@ 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);
@@ -4269,6 +4271,7 @@ 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);
@@ -5820,12 +5823,14 @@ 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)
@@ -5903,6 +5908,7 @@ 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);
@@ -9527,6 +9533,7 @@ 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;
|
