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 <stddef.h>
  32 #include <sys/types.h>
  33 #include <unistd.h>
  34 #include <lttng/ust-events.h>
  35 #include <lttng/ust-tracer.h>
  36 #include <lttng/ringbuffer-config.h>
  37 #include "../libringbuffer/getcpu.h"
  38
  39 static
  40 size_t cpu_id_get_size(struct lttng_ctx_field *field, size_t offset)
  41 {
  42         size_t size = 0;
  43
  44         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  45         size += sizeof(int);
  46         return size;
  47 }
  48
  49 static
  50 void cpu_id_record(struct lttng_ctx_field *field,
  51                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
  52                  struct lttng_channel *chan)
  53 {
  54         int cpu;
  55
  56         cpu = lttng_ust_get_cpu();
  57         lib_ring_buffer_align_ctx(ctx, lttng_alignof(cpu));
  58         chan->ops->event_write(ctx, &cpu, sizeof(cpu));
  59 }
  60
  61 static
  62 void cpu_id_get_value(struct lttng_ctx_field *field,
  63                 struct lttng_ctx_value *value)
  64 {
  65         value->u.s64 = lttng_ust_get_cpu();
  66 }
  67
  68 int lttng_add_cpu_id_to_ctx(struct lttng_ctx **ctx)
  69 {
  70         struct lttng_ctx_field *field;
  71
  72         field = lttng_append_context(ctx);
  73         if (!field)
  74                 return -ENOMEM;
  75         if (lttng_find_context(*ctx, "cpu_id")) {
  76                 lttng_remove_context_field(ctx, field);
  77                 return -EEXIST;
  78         }
  79         field->event_field.name = "cpu_id";
  80         field->event_field.type.atype = atype_integer;
  81         field->event_field.type.u.basic.integer.size = sizeof(int) * CHAR_BIT;
  82         field->event_field.type.u.basic.integer.alignment = lttng_alignof(int) * CHAR_BIT;
  83         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(int);
  84         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  85         field->event_field.type.u.basic.integer.base = 10;
  86         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
  87         field->get_size = cpu_id_get_size;
  88         field->record = cpu_id_record;
  89         field->get_value = cpu_id_get_value;
  90         lttng_context_update(*ctx);
  91         return 0;
  92 }