1 /**
2 * @file nmi_timer_int.c
3 *
4 * @remark Copyright 2011 Advanced Micro Devices, Inc.
5 *
6 * @author Robert Richter <robert.richter@amd.com>
7 */
8
9 #include <linux/init.h>
10 #include <linux/smp.h>
11 #include <linux/errno.h>
12 #include <linux/oprofile.h>
13 #include <linux/perf_event.h>
14
15 #ifdef CONFIG_OPROFILE_NMI_TIMER
16
17 static DEFINE_PER_CPU(struct perf_event *, nmi_timer_events);
18 static int ctr_running;
19
20 static struct perf_event_attr nmi_timer_attr = {
21 .type = PERF_TYPE_HARDWARE,
22 .config = PERF_COUNT_HW_CPU_CYCLES,
23 .size = sizeof(struct perf_event_attr),
24 .pinned = 1,
25 .disabled = 1,
26 };
27
nmi_timer_callback(struct perf_event * event,struct perf_sample_data * data,struct pt_regs * regs)28 static void nmi_timer_callback(struct perf_event *event,
29 struct perf_sample_data *data,
30 struct pt_regs *regs)
31 {
32 event->hw.interrupts = 0; /* don't throttle interrupts */
33 oprofile_add_sample(regs, 0);
34 }
35
nmi_timer_start_cpu(int cpu)36 static int nmi_timer_start_cpu(int cpu)
37 {
38 struct perf_event *event = per_cpu(nmi_timer_events, cpu);
39
40 if (!event) {
41 event = perf_event_create_kernel_counter(&nmi_timer_attr, cpu, NULL,
42 nmi_timer_callback, NULL);
43 if (IS_ERR(event))
44 return PTR_ERR(event);
45 per_cpu(nmi_timer_events, cpu) = event;
46 }
47
48 if (event && ctr_running)
49 perf_event_enable(event);
50
51 return 0;
52 }
53
nmi_timer_stop_cpu(int cpu)54 static void nmi_timer_stop_cpu(int cpu)
55 {
56 struct perf_event *event = per_cpu(nmi_timer_events, cpu);
57
58 if (event && ctr_running)
59 perf_event_disable(event);
60 }
61
nmi_timer_cpu_notifier(struct notifier_block * b,unsigned long action,void * data)62 static int nmi_timer_cpu_notifier(struct notifier_block *b, unsigned long action,
63 void *data)
64 {
65 int cpu = (unsigned long)data;
66 switch (action) {
67 case CPU_DOWN_FAILED:
68 case CPU_ONLINE:
69 nmi_timer_start_cpu(cpu);
70 break;
71 case CPU_DOWN_PREPARE:
72 nmi_timer_stop_cpu(cpu);
73 break;
74 }
75 return NOTIFY_DONE;
76 }
77
78 static struct notifier_block nmi_timer_cpu_nb = {
79 .notifier_call = nmi_timer_cpu_notifier
80 };
81
nmi_timer_start(void)82 static int nmi_timer_start(void)
83 {
84 int cpu;
85
86 get_online_cpus();
87 ctr_running = 1;
88 for_each_online_cpu(cpu)
89 nmi_timer_start_cpu(cpu);
90 put_online_cpus();
91
92 return 0;
93 }
94
nmi_timer_stop(void)95 static void nmi_timer_stop(void)
96 {
97 int cpu;
98
99 get_online_cpus();
100 for_each_online_cpu(cpu)
101 nmi_timer_stop_cpu(cpu);
102 ctr_running = 0;
103 put_online_cpus();
104 }
105
nmi_timer_shutdown(void)106 static void nmi_timer_shutdown(void)
107 {
108 struct perf_event *event;
109 int cpu;
110
111 cpu_notifier_register_begin();
112 __unregister_cpu_notifier(&nmi_timer_cpu_nb);
113 for_each_possible_cpu(cpu) {
114 event = per_cpu(nmi_timer_events, cpu);
115 if (!event)
116 continue;
117 perf_event_disable(event);
118 per_cpu(nmi_timer_events, cpu) = NULL;
119 perf_event_release_kernel(event);
120 }
121
122 cpu_notifier_register_done();
123 }
124
nmi_timer_setup(void)125 static int nmi_timer_setup(void)
126 {
127 int cpu, err;
128 u64 period;
129
130 /* clock cycles per tick: */
131 period = (u64)cpu_khz * 1000;
132 do_div(period, HZ);
133 nmi_timer_attr.sample_period = period;
134
135 cpu_notifier_register_begin();
136 err = __register_cpu_notifier(&nmi_timer_cpu_nb);
137 if (err)
138 goto out;
139
140 /* can't attach events to offline cpus: */
141 for_each_online_cpu(cpu) {
142 err = nmi_timer_start_cpu(cpu);
143 if (err) {
144 cpu_notifier_register_done();
145 nmi_timer_shutdown();
146 return err;
147 }
148 }
149
150 out:
151 cpu_notifier_register_done();
152 return err;
153 }
154
op_nmi_timer_init(struct oprofile_operations * ops)155 int __init op_nmi_timer_init(struct oprofile_operations *ops)
156 {
157 int err = 0;
158
159 err = nmi_timer_setup();
160 if (err)
161 return err;
162 nmi_timer_shutdown(); /* only check, don't alloc */
163
164 ops->create_files = NULL;
165 ops->setup = nmi_timer_setup;
166 ops->shutdown = nmi_timer_shutdown;
167 ops->start = nmi_timer_start;
168 ops->stop = nmi_timer_stop;
169 ops->cpu_type = "timer";
170
171 printk(KERN_INFO "oprofile: using NMI timer interrupt.\n");
172
173 return 0;
174 }
175
176 #endif
177