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 <lttng/ust-events.h>
  20 #include <lttng/ust-tracer.h>
  21 #include <lttng/ringbuffer-config.h>
  22 #include "../libringbuffer/getcpu.h"
  23
  24 #include "context-internal.h"
  25
  26 static
  27 size_t cpu_id_get_size(struct lttng_ctx_field *field, size_t offset)
  28 {
  29         size_t size = 0;
  30
  31         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  32         size += sizeof(int);
  33         return size;
  34 }
  35
  36 static
  37 void cpu_id_record(struct lttng_ctx_field *field,
  38                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
  39                  struct lttng_channel *chan)
  40 {
  41         int cpu;
  42
  43         cpu = lttng_ust_get_cpu();
  44         lib_ring_buffer_align_ctx(ctx, lttng_alignof(cpu));
  45         chan->ops->event_write(ctx, &cpu, sizeof(cpu));
  46 }
  47
  48 static
  49 void cpu_id_get_value(struct lttng_ctx_field *field,
  50                 struct lttng_ctx_value *value)
  51 {
  52         value->u.s64 = lttng_ust_get_cpu();
  53 }
  54
  55 int lttng_add_cpu_id_to_ctx(struct lttng_ctx **ctx)
  56 {
  57         struct lttng_ctx_field *field;
  58
  59         field = lttng_append_context(ctx);
  60         if (!field)
  61                 return -ENOMEM;
  62         if (lttng_find_context(*ctx, "cpu_id")) {
  63                 lttng_remove_context_field(ctx, field);
  64                 return -EEXIST;
  65         }
  66         field->event_field.name = "cpu_id";
  67         field->event_field.type.atype = atype_integer;
  68         field->event_field.type.u.integer.size = sizeof(int) * CHAR_BIT;
  69         field->event_field.type.u.integer.alignment = lttng_alignof(int) * CHAR_BIT;
  70         field->event_field.type.u.integer.signedness = lttng_is_signed_type(int);
  71         field->event_field.type.u.integer.reverse_byte_order = 0;
  72         field->event_field.type.u.integer.base = 10;
  73         field->event_field.type.u.integer.encoding = lttng_encode_none;
  74         field->get_size = cpu_id_get_size;
  75         field->record = cpu_id_record;
  76         field->get_value = cpu_id_get_value;
  77         lttng_context_update(*ctx);
  78         return 0;
  79 }