Root/drivers/oprofile/nmi_timer_int.c

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
17static DEFINE_PER_CPU(struct perf_event *, nmi_timer_events);
18static int ctr_running;
19
20static 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
28static 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
36static 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
54static 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
62static 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
78static struct notifier_block nmi_timer_cpu_nb = {
79    .notifier_call = nmi_timer_cpu_notifier
80};
81
82static 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
95static 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
106static void nmi_timer_shutdown(void)
107{
108    struct perf_event *event;
109    int cpu;
110
111    get_online_cpus();
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    put_online_cpus();
123}
124
125static 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    get_online_cpus();
136    err = register_cpu_notifier(&nmi_timer_cpu_nb);
137    if (err)
138        goto out;
139    /* can't attach events to offline cpus: */
140    for_each_online_cpu(cpu) {
141        err = nmi_timer_start_cpu(cpu);
142        if (err)
143            break;
144    }
145    if (err)
146        nmi_timer_shutdown();
147out:
148    put_online_cpus();
149    return err;
150}
151
152int __init op_nmi_timer_init(struct oprofile_operations *ops)
153{
154    int err = 0;
155
156    err = nmi_timer_setup();
157    if (err)
158        return err;
159    nmi_timer_shutdown(); /* only check, don't alloc */
160
161    ops->create_files = NULL;
162    ops->setup = nmi_timer_setup;
163    ops->shutdown = nmi_timer_shutdown;
164    ops->start = nmi_timer_start;
165    ops->stop = nmi_timer_stop;
166    ops->cpu_type = "timer";
167
168    printk(KERN_INFO "oprofile: using NMI timer interrupt.\n");
169
170    return 0;
171}
172
173#endif
174

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