liblttng-ust/lttng-context-cpu-id.c

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2009-2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * LTTng UST CPU id context.
   7  *
   8  * Note: threads can be migrated at any point while executing the
   9  * tracepoint probe. This means the CPU id field (and filter) is only
  10  * statistical. For instance, even though a user might select a
  11  * cpu_id==1 filter, there may be few events recorded into the channel
  12  * appearing from other CPUs, due to migration.
  13  */
  14
  15 #define _LGPL_SOURCE
  16 #include <stddef.h>
  17 #include <sys/types.h>
  18 #include <unistd.h>
  19 #include <limits.h>
  20 #include <lttng/ust-events.h>
  21 #include <lttng/ust-tracer.h>
  22 #include "../libringbuffer/getcpu.h"
  23 #include <lttng/ringbuffer-context.h>
  24
  25 #include "context-internal.h"
  26
  27 static
  28 size_t cpu_id_get_size(struct lttng_ust_ctx_field *field, size_t offset)
  29 {
  30         size_t size = 0;
  31
  32         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  33         size += sizeof(int);
  34         return size;
  35 }
  36
  37 static
  38 void cpu_id_record(struct lttng_ust_ctx_field *field,
  39                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
  40                  struct lttng_ust_channel_buffer *chan)
  41 {
  42         int cpu;
  43
  44         cpu = lttng_ust_get_cpu();
  45         lib_ring_buffer_align_ctx(ctx, lttng_alignof(cpu));
  46         chan->ops->event_write(ctx, &cpu, sizeof(cpu));
  47 }
  48
  49 static
  50 void cpu_id_get_value(struct lttng_ust_ctx_field *field,
  51                 struct lttng_ust_ctx_value *value)
  52 {
  53         value->u.s64 = lttng_ust_get_cpu();
  54 }
  55
  56 int lttng_add_cpu_id_to_ctx(struct lttng_ust_ctx **ctx)
  57 {
  58         struct lttng_ust_ctx_field *field;
  59         struct lttng_ust_type_common *type;
  60         int ret;
  61
  62         type = lttng_ust_create_type_integer(sizeof(int) * CHAR_BIT,
  63                         lttng_alignof(int) * CHAR_BIT,
  64                         lttng_ust_is_signed_type(int),
  65                         BYTE_ORDER, 10);
  66         if (!type)
  67                 return -ENOMEM;
  68         field = lttng_append_context(ctx);
  69         if (!field) {
  70                 ret = -ENOMEM;
  71                 goto error_context;
  72         }
  73         if (lttng_find_context(*ctx, "cpu_id")) {
  74                 ret = -EEXIST;
  75                 goto error_find_context;
  76         }
  77         field->event_field->name = strdup("cpu_id");
  78         if (!field->event_field->name) {
  79                 ret = -ENOMEM;
  80                 goto error_name;
  81         }
  82         field->event_field->type = type;
  83         field->get_size = cpu_id_get_size;
  84         field->record = cpu_id_record;
  85         field->get_value = cpu_id_get_value;
  86         lttng_context_update(*ctx);
  87         return 0;
  88
  89 error_name:
  90 error_find_context:
  91         lttng_remove_context_field(ctx, field);
  92 error_context:
  93         lttng_ust_destroy_type(type);
  94         return ret;
  95 }