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_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
  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
  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
 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
 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
 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