drivers/oprofile/cpu_buffer.h

   1 /**
   2  * @file cpu_buffer.h
   3  *
   4  * @remark Copyright 2002 OProfile authors
   5  * @remark Read the file COPYING
   6  *
   7  * @author John Levon <levon@movementarian.org>
   8  */
   9
  10 #ifndef OPROFILE_CPU_BUFFER_H
  11 #define OPROFILE_CPU_BUFFER_H
  12
  13 #include <linux/types.h>
  14 #include <linux/spinlock.h>
  15 #include <linux/workqueue.h>
  16 #include <linux/cache.h>
  17 #include <linux/sched.h>
  18
  19 struct task_struct;
  20
  21 int alloc_cpu_buffers(void);
  22 void free_cpu_buffers(void);
  23
  24 void start_cpu_work(void);
  25 void end_cpu_work(void);
  26
  27 /* CPU buffer is composed of such entries (which are
  28  * also used for context switch notes)
  29  */
  30 struct op_sample {
  31         unsigned long eip;
  32         unsigned long event;
  33 };
  34
  35 struct oprofile_cpu_buffer {
  36         volatile unsigned long head_pos;
  37         volatile unsigned long tail_pos;
  38         unsigned long buffer_size;
  39         struct task_struct *last_task;
  40         int last_is_kernel;
  41         int tracing;
  42         struct op_sample *buffer;
  43         unsigned long sample_received;
  44         unsigned long sample_lost_overflow;
  45         unsigned long backtrace_aborted;
  46         unsigned long sample_invalid_eip;
  47         int cpu;
  48         struct delayed_work work;
  49 };
  50
  51 DECLARE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
  52
  53 void cpu_buffer_reset(struct oprofile_cpu_buffer *cpu_buf);
  54
  55 static inline
  56 struct op_sample *cpu_buffer_write_entry(struct oprofile_cpu_buffer *cpu_buf)
  57 {
  58         return &cpu_buf->buffer[cpu_buf->head_pos];
  59 }
  60
  61 static inline
  62 void cpu_buffer_write_commit(struct oprofile_cpu_buffer *b)
  63 {
  64         unsigned long new_head = b->head_pos + 1;
  65
  66         /*
  67          * Ensure anything written to the slot before we increment is
  68          * visible
  69          */
  70         wmb();
  71
  72         if (new_head < b->buffer_size)
  73                 b->head_pos = new_head;
  74         else
  75                 b->head_pos = 0;
  76 }
  77
  78 static inline
  79 struct op_sample *cpu_buffer_read_entry(struct oprofile_cpu_buffer *cpu_buf)
  80 {
  81         return &cpu_buf->buffer[cpu_buf->tail_pos];
  82 }
  83
  84 /* "acquire" as many cpu buffer slots as we can */
  85 static inline
  86 unsigned long cpu_buffer_entries(struct oprofile_cpu_buffer *b)
  87 {
  88         unsigned long head = b->head_pos;
  89         unsigned long tail = b->tail_pos;
  90
  91         /*
  92          * Subtle. This resets the persistent last_task
  93          * and in_kernel values used for switching notes.
  94          * BUT, there is a small window between reading
  95          * head_pos, and this call, that means samples
  96          * can appear at the new head position, but not
  97          * be prefixed with the notes for switching
  98          * kernel mode or a task switch. This small hole
  99          * can lead to mis-attribution or samples where
 100          * we don't know if it's in the kernel or not,
 101          * at the start of an event buffer.
 102          */
 103         cpu_buffer_reset(b);
 104
 105         if (head >= tail)
 106                 return head - tail;
 107
 108         return head + (b->buffer_size - tail);
 109 }
 110
 111 /* transient events for the CPU buffer -> event buffer */
 112 #define CPU_IS_KERNEL 1
 113 #define CPU_TRACE_BEGIN 2
 114 #define IBS_FETCH_BEGIN 3
 115 #define IBS_OP_BEGIN    4
 116
 117 #endif /* OPROFILE_CPU_BUFFER_H */