liblttng-ust/lttng-context-vpid.c

   1 /*
   2  * (C) Copyright        2009-2011 -
   3  *              Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * LTTng UST vpid context.
   6  *
   7  * Dual LGPL v2.1/GPL v2 license.
   8  */
   9
  10 #include <sys/types.h>
  11 #include <unistd.h>
  12 #include <lttng/ust-events.h>
  13 #include <lttng/ust-tracer.h>
  14 #include <lttng/ringbuffer-config.h>
  15
  16 #ifdef __linux__
  17 static inline
  18 pid_t wrapper_getpid(void)
  19 {
  20         return getpid();
  21 }
  22
  23 void lttng_context_vpid_reset(void)
  24 {
  25 }
  26 #else
  27 /*
  28  * We cache the result to ensure we don't trigger a system call for
  29  * each event.
  30  */
  31 static pid_t cached_vpid;
  32
  33 static inline
  34 pid_t wrapper_getpid(void)
  35 {
  36         if (caa_unlikely(!cached_vpid))
  37                 cached_vpid = getpid();
  38         return cached_vpid;
  39 }
  40
  41 /*
  42  * Upon fork or clone, the PID assigned to our thread is not the same as
  43  * we kept in cache.
  44  */
  45 void lttng_context_vpid_reset(void)
  46 {
  47         cached_vpid = 0;
  48 }
  49 #endif
  50
  51 static
  52 size_t vpid_get_size(size_t offset)
  53 {
  54         size_t size = 0;
  55
  56         size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
  57         size += sizeof(pid_t);
  58         return size;
  59 }
  60
  61 static
  62 void vpid_record(struct lttng_ctx_field *field,
  63                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
  64                  struct ltt_channel *chan)
  65 {
  66         pid_t pid;
  67
  68         pid = wrapper_getpid();
  69         lib_ring_buffer_align_ctx(ctx, lttng_alignof(pid));
  70         chan->ops->event_write(ctx, &pid, sizeof(pid));
  71 }
  72
  73 int lttng_add_vpid_to_ctx(struct lttng_ctx **ctx)
  74 {
  75         struct lttng_ctx_field *field;
  76
  77         field = lttng_append_context(ctx);
  78         if (!field)
  79                 return -ENOMEM;
  80         if (lttng_find_context(*ctx, "vpid")) {
  81                 lttng_remove_context_field(ctx, field);
  82                 return -EEXIST;
  83         }
  84         field->event_field.name = "vpid";
  85         field->event_field.type.atype = atype_integer;
  86         field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
  87         field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
  88         field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
  89         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
  90         field->event_field.type.u.basic.integer.base = 10;
  91         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
  92         field->get_size = vpid_get_size;
  93         field->record = vpid_record;
  94         return 0;
  95 }