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
  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
  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
  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
  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
  62 static int nmi_timer_cpu_online(unsigned int cpu)
  63 {
  64         nmi_timer_start_cpu(cpu);
  65         return 0;
  66 }
  67 static int nmi_timer_cpu_predown(unsigned int cpu)
  68 {
  69         nmi_timer_stop_cpu(cpu);
  70         return 0;
  71 }
  72
  73 static int nmi_timer_start(void)
  74 {
  75         int cpu;
  76
  77         get_online_cpus();
  78         ctr_running = 1;
  79         for_each_online_cpu(cpu)
  80                 nmi_timer_start_cpu(cpu);
  81         put_online_cpus();
  82
  83         return 0;
  84 }
  85
  86 static void nmi_timer_stop(void)
  87 {
  88         int cpu;
  89
  90         get_online_cpus();
  91         for_each_online_cpu(cpu)
  92                 nmi_timer_stop_cpu(cpu);
  93         ctr_running = 0;
  94         put_online_cpus();
  95 }
  96
  97 static enum cpuhp_state hp_online;
  98
  99 static void nmi_timer_shutdown(void)
 100 {
 101         struct perf_event *event;
 102         int cpu;
 103
 104         cpuhp_remove_state(hp_online);
 105         for_each_possible_cpu(cpu) {
 106                 event = per_cpu(nmi_timer_events, cpu);
 107                 if (!event)
 108                         continue;
 109                 perf_event_disable(event);
 110                 per_cpu(nmi_timer_events, cpu) = NULL;
 111                 perf_event_release_kernel(event);
 112         }
 113 }
 114
 115 static int nmi_timer_setup(void)
 116 {
 117         int err;
 118         u64 period;
 119
 120         /* clock cycles per tick: */
 121         period = (u64)cpu_khz * 1000;
 122         do_div(period, HZ);
 123         nmi_timer_attr.sample_period = period;
 124
 125         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "oprofile/nmi:online",
 126                                 nmi_timer_cpu_online, nmi_timer_cpu_predown);
 127         if (err < 0) {
 128                 nmi_timer_shutdown();
 129                 return err;
 130         }
 131         hp_online = err;
 132         return 0;
 133 }
 134
 135 int __init op_nmi_timer_init(struct oprofile_operations *ops)
 136 {
 137         int err = 0;
 138
 139         err = nmi_timer_setup();
 140         if (err)
 141                 return err;
 142         nmi_timer_shutdown();           /* only check, don't alloc */
 143
 144         ops->create_files       = NULL;
 145         ops->setup              = nmi_timer_setup;
 146         ops->shutdown           = nmi_timer_shutdown;
 147         ops->start              = nmi_timer_start;
 148         ops->stop               = nmi_timer_stop;
 149         ops->cpu_type           = "timer";
 150
 151         printk(KERN_INFO "oprofile: using NMI timer interrupt.\n");
 152
 153         return 0;
 154 }
 155
 156 #endif