1 /******************************************************************************
2 * common/softirq.c
3 *
4 * Softirqs in Xen are only executed in an outermost activation (e.g., never
5 * within an interrupt activation). This simplifies some things and generally
6 * seems a good thing.
7 *
8 * Copyright (c) 2003, K A Fraser
9 * Copyright (c) 1992, Linus Torvalds
10 */
11
12 #include <xen/init.h>
13 #include <xen/mm.h>
14 #include <xen/preempt.h>
15 #include <xen/sched.h>
16 #include <xen/rcupdate.h>
17 #include <xen/softirq.h>
18
19 #ifndef __ARCH_IRQ_STAT
20 irq_cpustat_t irq_stat[NR_CPUS];
21 #endif
22
23 static softirq_handler softirq_handlers[NR_SOFTIRQS];
24
25 static DEFINE_PER_CPU(cpumask_t, batch_mask);
26 static DEFINE_PER_CPU(unsigned int, batching);
27
__do_softirq(unsigned long ignore_mask)28 static void __do_softirq(unsigned long ignore_mask)
29 {
30 unsigned int i, cpu;
31 unsigned long pending;
32 bool rcu_allowed = !(ignore_mask & (1UL << RCU_SOFTIRQ));
33
34 ASSERT(!rcu_allowed || rcu_quiesce_allowed());
35
36 for ( ; ; )
37 {
38 /*
39 * Initialise @cpu on every iteration: SCHEDULE_SOFTIRQ or
40 * SCHED_SLAVE_SOFTIRQ may move us to another processor.
41 */
42 cpu = smp_processor_id();
43
44 if ( rcu_allowed && rcu_pending(cpu) )
45 rcu_check_callbacks(cpu);
46
47 if ( ((pending = (softirq_pending(cpu) & ~ignore_mask)) == 0)
48 || cpu_is_offline(cpu) )
49 break;
50
51 i = ffsl(pending) - 1;
52 clear_bit(i, &softirq_pending(cpu));
53 (*softirq_handlers[i])();
54 }
55 }
56
process_pending_softirqs(void)57 void process_pending_softirqs(void)
58 {
59 /* Do not enter scheduler as it can preempt the calling context. */
60 unsigned long ignore_mask = (1UL << SCHEDULE_SOFTIRQ) |
61 (1UL << SCHED_SLAVE_SOFTIRQ);
62
63 /* Block RCU processing in case of rcu_read_lock() held. */
64 if ( !rcu_quiesce_allowed() )
65 ignore_mask |= 1UL << RCU_SOFTIRQ;
66
67 ASSERT(!in_irq() && local_irq_is_enabled());
68 __do_softirq(ignore_mask);
69 }
70
do_softirq(void)71 void do_softirq(void)
72 {
73 ASSERT_NOT_IN_ATOMIC();
74 __do_softirq(0);
75 }
76
open_softirq(int nr,softirq_handler handler)77 void open_softirq(int nr, softirq_handler handler)
78 {
79 ASSERT(nr < NR_SOFTIRQS);
80 softirq_handlers[nr] = handler;
81 }
82
cpumask_raise_softirq(const cpumask_t * mask,unsigned int nr)83 void cpumask_raise_softirq(const cpumask_t *mask, unsigned int nr)
84 {
85 unsigned int cpu, this_cpu = smp_processor_id();
86 cpumask_t send_mask, *raise_mask;
87
88 if ( !per_cpu(batching, this_cpu) || in_irq() )
89 {
90 cpumask_clear(&send_mask);
91 raise_mask = &send_mask;
92 }
93 else
94 raise_mask = &per_cpu(batch_mask, this_cpu);
95
96 for_each_cpu(cpu, mask)
97 if ( !arch_set_softirq(nr, cpu) && cpu != this_cpu )
98 __cpumask_set_cpu(cpu, raise_mask);
99
100 if ( raise_mask == &send_mask )
101 smp_send_event_check_mask(raise_mask);
102 }
103
cpu_raise_softirq(unsigned int cpu,unsigned int nr)104 void cpu_raise_softirq(unsigned int cpu, unsigned int nr)
105 {
106 unsigned int this_cpu = smp_processor_id();
107
108 if ( arch_set_softirq(nr, cpu) || cpu == this_cpu )
109 return;
110
111 if ( !per_cpu(batching, this_cpu) || in_irq() )
112 smp_send_event_check_cpu(cpu);
113 else
114 __cpumask_set_cpu(cpu, &per_cpu(batch_mask, this_cpu));
115 }
116
cpu_raise_softirq_batch_begin(void)117 void cpu_raise_softirq_batch_begin(void)
118 {
119 ++this_cpu(batching);
120 }
121
cpu_raise_softirq_batch_finish(void)122 void cpu_raise_softirq_batch_finish(void)
123 {
124 unsigned int cpu, this_cpu = smp_processor_id();
125 cpumask_t *mask = &per_cpu(batch_mask, this_cpu);
126
127 ASSERT(per_cpu(batching, this_cpu));
128 for_each_cpu ( cpu, mask )
129 if ( !softirq_pending(cpu) )
130 __cpumask_clear_cpu(cpu, mask);
131 smp_send_event_check_mask(mask);
132 cpumask_clear(mask);
133 --per_cpu(batching, this_cpu);
134 }
135
raise_softirq(unsigned int nr)136 void raise_softirq(unsigned int nr)
137 {
138 unsigned int cpu = smp_processor_id();
139
140 set_bit(nr, &softirq_pending(cpu));
141 }
142
143 /*
144 * Local variables:
145 * mode: C
146 * c-file-style: "BSD"
147 * c-basic-offset: 4
148 * tab-width: 4
149 * indent-tabs-mode: nil
150 * End:
151 */
152