src/lttng-context-prio.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-prio.c
   4  *
   5  * LTTng priority context.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <linux/sched.h>
  13 #include <lttng/events.h>
  14 #include <lttng/events-internal.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <lttng/tracer.h>
  18
  19 /*
  20  * task_prio() has been implemented as p->prio - MAX_RT_PRIO since at
  21  * least kernel v3.0.
  22  */
  23 static
  24 int wrapper_task_prio(struct task_struct *p)
  25 {
  26         return p->prio - MAX_RT_PRIO;
  27 }
  28
  29 static
  30 size_t prio_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  31 {
  32         size_t size = 0;
  33
  34         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  35         size += sizeof(int);
  36         return size;
  37 }
  38
  39 static
  40 void prio_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  41                 struct lttng_kernel_ring_buffer_ctx *ctx,
  42                 struct lttng_kernel_channel_buffer *chan)
  43 {
  44         int prio;
  45
  46         prio = wrapper_task_prio(current);
  47         chan->ops->event_write(ctx, &prio, sizeof(prio), lttng_alignof(prio));
  48 }
  49
  50 static
  51 void prio_get_value(void *priv,
  52                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  53                 struct lttng_ctx_value *value)
  54 {
  55         value->u.s64 = wrapper_task_prio(current);
  56 }
  57
  58 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  59         lttng_kernel_static_event_field("prio",
  60                 lttng_kernel_static_type_integer_from_type(int, __BYTE_ORDER, 10),
  61                 false, false),
  62         prio_get_size,
  63         prio_record,
  64         prio_get_value,
  65         NULL, NULL);
  66
  67 int lttng_add_prio_to_ctx(struct lttng_kernel_ctx **ctx)
  68 {
  69         int ret;
  70
  71         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  72                 return -EEXIST;
  73         ret = lttng_kernel_context_append(ctx, ctx_field);
  74         wrapper_vmalloc_sync_mappings();
  75         return ret;
  76 }
  77 EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx);