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

   1 /*
   2  * lttng-context-cpu-id.c
   3  *
   4  * LTTng UST CPU id context.
   5  *
   6  * Note: threads can be migrated at any point while executing the
   7  * tracepoint probe. This means the CPU id field (and filter) is only
   8  * statistical. For instance, even though a user might select a
   9  * cpu_id==1 filter, there may be few events recorded into the channel
  10  * appearing from other CPUs, due to migration.
  11  *
  12  * Copyright (C) 2009-2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  13  *
  14  * This library is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU Lesser General Public
  16  * License as published by the Free Software Foundation; only
  17  * version 2.1 of the License.
  18  *
  19  * This library is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  22  * Lesser General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Lesser General Public
  25  * License along with this library; if not, write to the Free Software
  26  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  27  */
  28
  29 #define _GNU_SOURCE
  30 #define _LGPL_SOURCE
  31 #include <sys/types.h>
  32 #include <unistd.h>
  33 #include <lttng/ust-events.h>
  34 #include <lttng/ust-tracer.h>
  35 #include <lttng/ringbuffer-config.h>
  36 #include "../libringbuffer/getcpu.h"
  37
  38 static
  39 size_t cpu_id_get_size(struct lttng_ctx_field *field, size_t offset)
  40 {
  41         size_t size = 0;
  42
  43         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  44         size += sizeof(int);
  45         return size;
  46 }
  47
  48 static
  49 void cpu_id_record(struct lttng_ctx_field *field,
  50                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
  51                  struct lttng_channel *chan)
  52 {
  53         int cpu;
  54
  55         cpu = lttng_ust_get_cpu();
  56         lib_ring_buffer_align_ctx(ctx, lttng_alignof(cpu));
  57         chan->ops->event_write(ctx, &cpu, sizeof(cpu));
  58 }
  59
  60 static
  61 void cpu_id_get_value(struct lttng_ctx_field *field,
  62                 struct lttng_ctx_value *value)
  63 {
  64         int cpu;
  65
  66         cpu = lttng_ust_get_cpu();
  67         value->u.s64 = cpu;
  68 }
  69
  70 int lttng_add_cpu_id_to_ctx(struct lttng_ctx **ctx)
  71 {
  72         struct lttng_ctx_field *field;
  73
  74         field = lttng_append_context(ctx);
  75         if (!field)
  76                 return -ENOMEM;
  77         if (lttng_find_context(*ctx, "cpu_id")) {
  78                 lttng_remove_context_field(ctx, field);
  79                 return -EEXIST;
  80         }
  81         field->event_field.name = "cpu_id";
  82         field->event_field.type.atype = atype_integer;
  83         field->event_field.type.u.basic.integer.size = sizeof(int) * CHAR_BIT;
  84         field->event_field.type.u.basic.integer.alignment = lttng_alignof(int) * CHAR_BIT;
  85         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(int);
  86         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  87         field->event_field.type.u.basic.integer.base = 10;
  88         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
  89         field->get_size = cpu_id_get_size;
  90         field->record = cpu_id_record;
  91         field->get_value = cpu_id_get_value;
  92         lttng_context_update(*ctx);
  93         return 0;
  94 }